Answer:
(x+4)^2 -25
Explanation:
x²+8x-9 in the form (x+k)² +h.
We need to complete the square.
x^2 +8x -9
Take the coefficient of x.
8
Divide by 2.
8/2 =4
Square it.
4^2 = 16
Add this then subtract i.
x^2 +8x+16 -16 -9
The x^2 +8x+16 becomes (x+4) ^2 and we can simplify the remaining terms.
(x+4)^2 -25