Question

What is the value of the expression `2x^2+ 3xy- 4y^2` when x=2 and y=-4?

Answer 1

`-80`

Explanation:

Substituting `2` for each occurrence of `x` in the expression and `-4` for each occurrence of `y` in the expression can calculating gives:

`(2*2^2) + (3*2*-4) - (4*-4^2)`

`(2*4) + (6*-4) - (4*16)`

`8 - 24 - 64`

`-16 - 64`

`-80`