SOLUTION: What is the value of the expression 2x squared + 3xy - 4y squared when x=2 and y=-4? A. -80 B. 80 C. -32 D. 32 My solution 8+3(2)(-4) - 4(-4) squared 8+(-24)-64 -32-64

Algebra ->  Polynomials-and-rational-expressions -> SOLUTION: What is the value of the expression 2x squared + 3xy - 4y squared when x=2 and y=-4? A. -80 B. 80 C. -32 D. 32 My solution 8+3(2)(-4) - 4(-4) squared 8+(-24)-64 -32-64       Log On


   

Question 183960: What is the value of the expression 2x squared + 3xy - 4y squared when x=2 and y=-4?
A. -80
B. 80
C. -32
D. 32
My solution
8+3(2)(-4) - 4(-4) squared
8+(-24)-64
-32-64 = -96
Help me! What am I doing wrong?
Found 2 solutions by stanbon, Alan3354:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
What is the value of the expression 2x squared + 3xy - 4y squared when x=2 and y=-4?
A. -80
B. 80
C. -32
D. 32
---------------------------
2x^2 + 3xy - 4y^2
-------------------------------------
2(2)^2 + 3*2*4 - 4*4^2
= 8 + 24 - 64
= -32
=======================
Cheers,
Stan H.

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
What is the value of the expression 2x squared + 3xy - 4y squared when x=2 and y=-4?
A. -80
B. 80
C. -32
D. 32
My solution
8+3(2)(-4) - 4(-4) squared
8+(-24)-64
-32-64 = -96 ::: 8 + (-24) is -16, not -32 :::
Help me! What am I doing wrong?
----------------------
2x^2 + 3xy - 4y^2
------------
2*4 + 3*2*(-4) - 4*(16)
8 - 24 - 64
= 8 - 88
= -80