Question

Why is (3,-5) not a solution to -x+4y=-15

Answer 1

C) It doesn’t satisfy either the top or bottom equations.


When we plug them into the top equation:
$- 3 + 4( - 5) = - 15$
Simplify:
$- 3 + ( - 20) = - 15 \\ \\ - 23= - 15$
Because the statement of -23 = -15 is wrong, the solution pair is wrong for the top equation.


When we plug them into the bottom equation:
$- 2(3) - 3( - 5) = - 8$
Simplify:
$- 6 - ( - 15) = - 8 \\ \\ 9 = - 8$
9 = -8 is not a valid statement, so the pair doesn't satisfy both of the equations.