Answer:
x = -4 or 2
Explanation:
-4x² + 10x − 40 = -9x²
First, move the x terms to one side and the constant to the other.
5x² + 10x = 40
Divide by the leading coefficient:
x² + 2x = 8
Take half of the b coefficient, square it, then add to both sides.
(2/2)² = 1
x² + 2x + 1 = 8 + 1
x² + 2x + 1 = 9
Factor the perfect square:
(x + 1)² = 9
Solve for x:
x + 1 = ±3
x = -1 ± 3
x = -4 or 2