Question

Which are the solutions of x2 = –5x + 8?

Answer 1

x = -2.5 ± √14.25

Explanation:

Add 5x to prepare for "completing the square."

x² +5x = 8

Add the square of half the x-coefficient:

x² +5x + 2.5² = 8 + 2.5²

(x +2.5)² = 14.25

Take the square root.

x +2.5 = ±√14.25

Subtract 2.5.

x = -2.5 ± √14.25 ≈ {-6.27492, 1.27592}