Question

Solve the equation by completing the square. 0 = 4x2 − 72x A. x = 0, 18 B. x = -72, 90 C. x = -90, 72 D. x = -18, 0

Answer 1

A. x = 0, 18

Explanation:

0 = 4x2 − 72x

4x^2 - 72x = 0

x^2 - 18x = 0

x^2 - 18x + 81 = 81

(x - 9)^2 = 81

x - 9 = 9 or x - 9 = -9

x = 18 or x = 0

Answer: A. x = 0, 18

Answer 2

A. x = 0, 18

Explanation:

Step 1: GCF

4(x² - 18x) = 0

x² -18x = 0

Step 2: Complete the Square

x² -18x + 81 = 0 + 81

(x - 9)² = 81

Step 3: Solve

√(x - 9)² = √81

x - 9 = ±9

x = 9±9, or x = 0, 18

And we have our answers!