# Concept derivation guides

299 concept teaching guides, separate from the 36,000 individual question derivations.

[Search all questions & derivations →](/en/explore/)

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Concept guide



## [Direct MSE without the decomposition formula](/en/derivations/derivation-mko-estimator-mean-squared-error-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Weight losses directly at every theta, leaving decomposition for later.

Mean squared error of an estimator

derivation-mko-estimator-mean-squared-error-01



Concept guide



## [The two-way point correspondence for slack variables](/en/derivations/derivation-mko-linear-program-standard-form-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Convert a fixed maximize/≤/nonnegative LP to equality slack form and verify both feasible-point directions and objective.

Standard form of a linear program

derivation-mko-linear-program-standard-form-01



Concept guide



## [Vertex covers and deletion certificates on a star](/en/derivations/derivation-mko-vertex-cover-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Audit covers edgewise and distinguish minimal from minimum.

Vertex cover

derivation-mko-vertex-cover-01



Concept guide



## [The correct image isomorphism for a nonsurjection](/en/derivations/derivation-mko-first-isomorphism-theorem-finite-groups-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

For f:C4 to C4,f(a)=2a mod 4, C4/{0,2} is isomorphic to {0,2}, not the full codomain C4.

First isomorphism theorem for finite groups

derivation-mko-first-isomorphism-theorem-finite-groups-01



Concept guide



## [Certifying the center from all commutation rows](/en/derivations/derivation-mko-finite-group-center-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Z(G)={e}, directly a normal subgroup; G is nonabelian and r is not central despite commuting with itself.

Center of a finite group

derivation-mko-finite-group-center-01



Concept guide



## [Bias-variance derivation with the cross term visible](/en/derivations/derivation-mko-bias-variance-decomposition-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Prove the decomposition symbol by symbol in one law and check both theta values.

Bias-variance decomposition

derivation-mko-bias-variance-decomposition-01



Concept guide



## [The weak-duality chain and a zero-gap optimality certificate](/en/derivations/derivation-mko-linear-program-duality-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Construct the full dual, check feasibility of x=(1,3), y=(1,1), and certify both optimal by zero gap.

Linear-programming duality

derivation-mko-linear-program-duality-01



Concept guide



## [All four cuts and an equal-value two-sided certificate](/en/derivations/derivation-mko-max-flow-min-cut-theorem-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Enumerate every s-t cut of a four-vertex network and give a feasible flow of value 5 together with a cut of capacity 5.

Max-flow min-cut theorem

derivation-mko-max-flow-min-cut-theorem-01



Concept guide



## [All eight subsets for minimum cover on P3](/en/derivations/derivation-mko-minimum-vertex-cover-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Classify every cover and all minimizers.

Minimum vertex cover

derivation-mko-minimum-vertex-cover-01



Concept guide



## [A complete finite reduction with preserved direction](/en/derivations/derivation-mko-many-one-reduction-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Check every x equivalence, composition and decider transfer.

Many-one reduction

derivation-mko-many-one-reduction-01



Concept guide



## [A complete contraction certificate on a finite metric](/en/derivations/derivation-mko-contraction-mapping-theorem-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Audit completeness, a unique fixed point and the error bound for a constant self-map on a three-point discrete metric.

Contraction mapping theorem

derivation-mko-contraction-mapping-theorem-01



Concept guide



## [A polynomial bracket and an exact intermediate value](/en/derivations/derivation-mko-intermediate-value-theorem-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Find value zero for f(x)=x^2-1 on [0,2], retaining endpoint and nonuniqueness boundaries.

Intermediate value theorem

derivation-mko-intermediate-value-theorem-01



Concept guide



## [An exact Lagrange remainder for a cubic](/en/derivations/derivation-mko-taylor-remainder-theorem-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

For f(x)=x^3, a=1, n=2, x=2, audit the exact remainder and a qualified derivative bound.

Taylor remainder theorem

derivation-mko-taylor-remainder-theorem-01



Concept guide



## [MLE with a positive-mass tie and an all-zero likelihood column](/en/derivations/derivation-mko-finite-maximum-likelihood-estimator-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Compute every argmax and a total estimator using a fixed tie rule.

Maximum-likelihood estimator in a finite model

derivation-mko-finite-maximum-likelihood-estimator-01



Concept guide



## [A sufficiency certificate from every fibre conditional law](/en/derivations/derivation-mko-finite-sufficient-statistic-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Audit invariance across theta on every positive-mass fibre, retaining undefined null conditions.

Sufficient statistic in a finite model

derivation-mko-finite-sufficient-statistic-01



Concept guide



## [All permutations and a Kahn trace for a three-vertex DAG](/en/derivations/derivation-mko-topological-ordering-dag-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

List every valid order and audit source-removal invariants.

Topological ordering of a directed acyclic graph

derivation-mko-topological-ordering-dag-01



Concept guide



## [The first power returning to one](/en/derivations/derivation-mko-multiplicative-order-mod-n-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

ord_8(-5)=ord_8(3)=2, with phi(8)=4 and 2 dividing 4 but not equal to it.

Multiplicative order modulo n

derivation-mko-multiplicative-order-mod-n-01



Concept guide



## [The direction of eventual comparison and finite prefixes](/en/derivations/derivation-mko-series-comparison-test-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Prove convergence using geometric upper comparison despite a finite prefix, and show divergent lower comparison.

Comparison tests for series

derivation-mko-series-comparison-test-01



Concept guide



## [Ratio limits, geometric domination and L=1](/en/derivations/derivation-mko-ratio-test-series-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Use complete rational ratios for L<1 convergence and L>1 divergence, then audit indecision at L=1.

Ratio test for series

derivation-mko-ratio-test-series-01



Concept guide



## [An epsilon/3 transfer through one fixed approximant](/en/derivations/derivation-mko-uniform-limit-continuity-theorem-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Prove uniform convergence of affine perturbations on [0,1] and transfer continuity step by step.

A uniform limit of continuous functions is continuous

derivation-mko-uniform-limit-continuity-theorem-01



Concept guide



## [Every open set in a four-point product](/en/derivations/derivation-mko-finite-product-topology-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Generate every product open from two Sierpinski factors and audit projections.

Finite product topology

derivation-mko-finite-product-topology-01



Concept guide



## [The full preimage condition determines the quotient topology](/en/derivations/derivation-mko-quotient-topology-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Compute a quotient topology for a three-to-two-point surjection and show an open-image failure.

Quotient topology

derivation-mko-quotient-topology-01



Concept guide



## [Universal paths and concatenation in a convex box](/en/derivations/derivation-mko-path-connected-space-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Prove [0,1]^2 path connected and audit a two-piece concatenation.

Path-connected space

derivation-mko-path-connected-space-01



Concept guide



## [Finding inclusion-maximal components from the complete subset table](/en/derivations/derivation-mko-topological-connected-component-01/?from=%2Fen%2Fderivations%2F%3Fpage%3D12)

Find every component of X={a,b,c}, tau={empty,{a},{b,c},X}.

Connected component of a topological space

derivation-mko-topological-connected-component-01





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