# Concept derivation guides

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

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

1 1 results · Page 1 of 1



Concept guide



## [Linear systems in two variables: the unique-solution formula, checking both rows, and consistency when D=0](/en/derivations/derivation-mko-system-linear-equations-01/?from=%2Fen%2Fderivations%2F%3Fq%3Dmko-system-linear-equations)

(I) Solve 2x+3y=7, x−y=1: prove the unique-solution formula when D=ae−bd≠0, solve, and check by substituting into both rows; (II) decide x+2y=3, 2x+4y=7; (III) decide x+2y=3, 2x+4y=6; and use (IV) 0x+0y=1, 0x+0y=2 to show that D and both Cramer numerators being zero does not imply infinitely many solutions.

Linear systems in two variables and degenerate constraints

derivation-mko-system-linear-equations-01





1 1 results · Page 1 of 1