Question

What is the value of the expression 2x2 + 3xy – 4y2 when x = 2 and y = - 4?

Answer 1

Please use " ^ " to denote exponentiation:  2x^2 + 3xy – 4y^2

Now let x=2 and y= -4:

2(2)^2 + 3(2)(-4) - 4(-4)^2 = 8 - 24 -4(16) = -16 - 4(16) = -5(16) = -80 (answer)