Answer:
48
Step-by-step explanation:
2x² + 3xy - 4y²
2 * 2² + 3 * 2 * (-4) - 4 x -4²
=48
-80
When x=2 and y= -4
2x² + 3xy - 4y² = 2(2)² + 3(2)(-4) - 4(-4)² = 8 - 24 -4(16) = -16 - 64 = -80
