Explore related knowledge and questions →
← Question derivation index · Original question batch
R0022-11858 · q-20261013-advance-20261025-r02-convex-function-0083
Use the one-variable quadratic f(t)=a*t²+b*t+c with coefficients [a,b,c]=[3, -5, -3], not ascending-power order. The declared interval [lower,upper]=[-5, 5] belongs to the function data. x=0/1, y=-3/1, lambda=8/10 must lie in the declared domain and closed unit weight interval. Give (coefficients,interval,x,y,lambda,weighted input,lhs=f(weighted input),rhs=weighted endpoint values,rhs−lhs,inequality passes?,nonconvexity_witness if the gap is negative, otherwise single_instance_only). Use exact rational arithmetic with reduced positive denominators; omit /1 for integers. A positive convexity certificate must cover all endpoint pairs in the convex domain and every lambda in [0,1]. One Jensen violation can refute convexity, but one successful instance cannot prove it.
G001 — Use the one-variable quadratic f(t)=a*t²+b*t+c with coefficients [a,b,c]=[3, -5, -3], not ascending-power order. The declared interval [lower,upper]=[-5, 5] belongs to the function data. x=0/1, y=-3/1, lambda=8/10 must lie in the declared domain and closed unit weight interval. Give (coefficients,interval,x,y,lambda,weighted input,lhs=f(weighted input),rhs=weighted endpoint values,rhs−lhs,inequality passes?,nonconvexity_witness if the gap is negative, otherwise single_instance_only). Use exact rational arithmetic with reduced positive denominators; omit /1 for integers. A positive convexity certificate must cover all endpoint pairs in the convex domain and every lambda in [0,1]. One Jensen violation can refute convexity, but one successful instance cannot prove it.Use the original question domain, assumptions and cited MKO definitions. This item has second-context mathematical and bilingual review, with the model, answer and every arithmetic step independently recomputed from the original parameters; the source question remains a candidate.
Before
declared interval record=[-5, 5]
After
ordered_nonempty=Yes;nondegenerate=Yes
Conditions: none
This nonempty-interval protocol uses lower≤upper;the nondegenerate certificate additionally needs lower<upper.A reversed record is unqualified,not a declaration that the abstract empty set is nonconvex.A singleton interval is convex.
Rule: interval_certificate_qualification_not_empty_set_nonconvexity · Uses: G001
Before
arbitrary x,y in [-5,5];0<=lambda<=1;z=lambda*x+(1-lambda)*y
After
z--5=lambda*(x--5)+(1-lambda)*(y--5)>=0;5-z=lambda*(5-x)+(1-lambda)*(5-y)>=0
Conditions: none
Both slacks are nonnegative sums,hence lower≤z≤upper for every endpoint pair and every permitted lambda.No sampling is used;endpoints and singleton cases are included.
Rule: interval_all_segments_slack_identity · Uses: G001, S001
Before
univariate quadratic coefficients=[3, -5, -3];order=[a,b,c]
After
f(t)=(3)*t^2+(-5)*t+(-3)
Conditions: none
These are quadratic,linear,constant coefficients in descending order,not the constant-first boundary-polynomial order.Retain zero leading coefficients.
Rule: quadratic_descending_coefficient_order · Uses: G001, S002
Before
f(t)=(3)*t^2+(-5)*t+(-3);z=lambda*x+(1-lambda)*y
After
rhs-lhs=(3)*(lambda*x^2+(1-lambda)*y^2-(lambda*x+(1-lambda)*y)^2)
Conditions: none
Expand both Jensen sides.The unit weight sum cancels the linear and constant terms exactly,leaving only the quadratic part.
Rule: jensen_linear_and_constant_terms_cancel · Uses: G001, S003
Before
lambda*x^2+(1-lambda)*y^2-(lambda*x+(1-lambda)*y)^2
After
lambda*(1-lambda)*(x-y)^2;full gap=(3)*lambda*(1-lambda)*(x-y)^2
Conditions: none
Expand the square and collect x²,xy,y².The coefficients are lambda(1−lambda),−2lambda(1−lambda),lambda(1−lambda),yielding the(x−y)^2 factor for all real endpoints.
Rule: jensen_gap_full_symbolic_factorization · Uses: G001, S004
Before
Jensen complementary weight := sub(1, 4/5)
After
Jensen complementary weight = 1/5
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S005
Before
Jensen weighted x := mul(4/5, 0)
After
Jensen weighted x = 0
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S006
Before
Jensen weighted y := mul(1/5, -3)
After
Jensen weighted y = -3/5
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S007
Before
Jensen weighted input := sum(0, -3/5)
After
Jensen weighted input = -3/5
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S008
Before
Jensen lhs point squared := mul(-3/5, -3/5)
After
Jensen lhs point squared = 9/25
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S009
Before
Jensen lhs quadratic term := mul(3, 9/25)
After
Jensen lhs quadratic term = 27/25
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S010
Before
Jensen lhs linear term := mul(-5, -3/5)
After
Jensen lhs linear term = 3
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S011
Before
Jensen lhs polynomial value := sum(27/25, 3, -3)
After
Jensen lhs polynomial value = 27/25
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S012
Before
Jensen left endpoint point squared := mul(0, 0)
After
Jensen left endpoint point squared = 0
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S013
Before
Jensen left endpoint quadratic term := mul(3, 0)
After
Jensen left endpoint quadratic term = 0
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S014
Before
Jensen left endpoint linear term := mul(-5, 0)
After
Jensen left endpoint linear term = 0
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S015
Before
Jensen left endpoint polynomial value := sum(0, 0, -3)
After
Jensen left endpoint polynomial value = -3
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S016
Before
Jensen right endpoint point squared := mul(-3, -3)
After
Jensen right endpoint point squared = 9
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S017
Before
Jensen right endpoint quadratic term := mul(3, 9)
After
Jensen right endpoint quadratic term = 27
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S018
Before
Jensen right endpoint linear term := mul(-5, -3)
After
Jensen right endpoint linear term = 15
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S019
Before
Jensen right endpoint polynomial value := sum(27, 15, -3)
After
Jensen right endpoint polynomial value = 39
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S020
Before
Jensen weighted left value := mul(4/5, -3)
After
Jensen weighted left value = -12/5
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S021
Before
Jensen weighted right value := mul(1/5, 39)
After
Jensen weighted right value = 39/5
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S022
Before
Jensen rhs := sum(-12/5, 39/5)
After
Jensen rhs = 27/5
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S023
Before
Jensen rhs minus lhs := sub(27/5, 27/25)
After
Jensen rhs minus lhs = 108/25
Conditions: none
Compute exactly from this step's original roles and established intermediates,retaining signs,denominators and coefficient order.
Rule: exact_rational_arithmetic · Uses: G001, S024
Before
qualified x=0;y=-3;lambda=4/5;lhs=27/25;rhs=27/5;gap=108/25
After
Jensen instance passes=Yes;scope=single_instance_only
Conditions: none
A negative gap at qualified endpoints and weight is a counterexample.Nonnegative proves only this instance;lambda0 or x=y can pass even for a nonconvex quadratic.
Rule: one_Jensen_instance_not_universal_positive_proof · Uses: G001, S025
S026 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.S025 · premise_and_result_audit — Recompute Jensen rhs minus lhs with exact rational arithmetic, not rounded decimals.S024 · premise_and_result_audit — Recompute Jensen rhs with exact rational arithmetic, not rounded decimals.S023 · premise_and_result_audit — Recompute Jensen weighted right value with exact rational arithmetic, not rounded decimals.S022 · premise_and_result_audit — Recompute Jensen weighted left value with exact rational arithmetic, not rounded decimals.S021 · premise_and_result_audit — Recompute Jensen right endpoint polynomial value with exact rational arithmetic, not rounded decimals.S020 · premise_and_result_audit — Recompute Jensen right endpoint linear term with exact rational arithmetic, not rounded decimals.S019 · premise_and_result_audit — Recompute Jensen right endpoint quadratic term with exact rational arithmetic, not rounded decimals.S018 · premise_and_result_audit — Recompute Jensen right endpoint point squared with exact rational arithmetic, not rounded decimals.S017 · premise_and_result_audit — Recompute Jensen left endpoint polynomial value with exact rational arithmetic, not rounded decimals.S016 · premise_and_result_audit — Recompute Jensen left endpoint linear term with exact rational arithmetic, not rounded decimals.S015 · premise_and_result_audit — Recompute Jensen left endpoint quadratic term with exact rational arithmetic, not rounded decimals.S014 · premise_and_result_audit — Recompute Jensen left endpoint point squared with exact rational arithmetic, not rounded decimals.S013 · premise_and_result_audit — Recompute Jensen lhs polynomial value with exact rational arithmetic, not rounded decimals.S012 · premise_and_result_audit — Recompute Jensen lhs linear term with exact rational arithmetic, not rounded decimals.S011 · premise_and_result_audit — Recompute Jensen lhs quadratic term with exact rational arithmetic, not rounded decimals.S010 · premise_and_result_audit — Recompute Jensen lhs point squared with exact rational arithmetic, not rounded decimals.S009 · premise_and_result_audit — Recompute Jensen weighted input with exact rational arithmetic, not rounded decimals.S008 · premise_and_result_audit — Recompute Jensen weighted y with exact rational arithmetic, not rounded decimals.S007 · premise_and_result_audit — Recompute Jensen weighted x with exact rational arithmetic, not rounded decimals.S006 · premise_and_result_audit — Recompute Jensen complementary weight with exact rational arithmetic, not rounded decimals.S005 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.S004 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.S003 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.S002 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.S001 · premise_and_result_audit — Check against the original data and this step's premises; a one-way implication is not an equivalence.([3, -5, -3], [-5, 5], 0, -3, 4/5, -3/5, 27/25, 27/5, 108/25, Yes, single_instance_only)
The full substitutions and premise checks give the original answer; source identity,format and status are unchanged.
Review date: 2026-10-26
Original questions, answers, step expressions, numeric ASTs and historical records are retained. Source candidate labels remain historical and are not overwritten as formal proof.
input commit: 0f7be61e2c22317a4075561dc822c87d881a50dboriginal question SHA-256: 8ac012fcfb1ddbcc98803bad902370a0f6ec00a0b9ca77d201e319cc331260d0candidate record SHA-256: 5b199af7f0ac44ac420bdae322db73ca4bee7caad48db5d65a0d84a90305a7b4semantic review receipt SHA-256: 94ec4350cf8b5e5c6c7701d536126eef20acb3a213e873ace4f5346d256b8facquestion-first witness SHA-256: 0beba165ffd367a7c96de3aa58344d572d01434cd2ef772fbb00342c1f50b01bLean: NOT_RUN · human review: NOT_PERFORMED