Question

what is the value expression 2x^2 + 3xy-4y^2 when x=2 and y=-4

Answer 1

2(2)^2+3(2)(-4)-4(-4)^2=
8-24-64

Answer 2

Just plug in 2 for every x and -4 for every y.
\[2(2) ^{2}+3(2)(-4)-4(-4)^{2}\]