Question

how do you....complete the square
-2((x^2)+3x-4)

Answer 1

x^2 + 3x - 4 is not a perfect square, but
x^2 + 3x + (3/2)^2 is a perfect square
3/2^2 = 9/4, which is 2.25
In order to add 2.25, you have to also subtract it so that you don't change the value:
-2((x^2)+3x + 2.25 - 2.25 -4)
Then simplify:
-2((x+3/2)^2 - 2.25-4)
-2((x+3/2)^2 - 6.25)

Answer 2

the original equation was f(x)=-2x^2-6x+8