Question

-3x 2 + 2y 2 + 5xy - 2y + 5x 2 - 3y 2 if x=2 and y=-1

Answer 1

if $x=2,y=1$ the formula becomes:
$-3(2)^2 + 2\times1^2 + 5(2) - 2 + 5(2)^2 - 3\times1^ 2\\=(-12+2)+(10-2)+(20-3)\\=(-10+8)+17\\=-2+17\\=15$