How do you solve this problem what is the value of the expression 2x squared plus 3xy - 4y squared when x equals 2 and Y equals 4?

x = 2 so x squared = 4 and 2x squared = 2 times 4 = 8;

y = 4 so xy = 2 times 4 = 8 and 3xy = 3 times 8 = 24;

y squared = 4 times 4 = 16 and 4y squared = 4 times 16 = 64;

so 8 + 24 - 64 = 32 - 64 = -32