Question

Solve the equation by completing the square. 0 = 4x2 − 72x

Answer 1

Answer:

B

Step-by-step explanation:

Given

4x² - 72x = 0 ← factor out 4 from each term

4(x² - 18x) = 0

To complete the square

add/subtract (half the coefficient of the x- term)² to x² - 18x

4(x² + 2(- 9)x + 81 - 81) = 0

4(x - 9)² - 4(81) = 0

4(x - 9)² - 324 = 0 ( add 324 to both sides )

4(x - 9)² = 324 ( divide both sides by 4 )

(x - 9)² = 81 ( take the square root of both sides )

x - 9 = ± $\sqrt{81}$ = ± 9 ( add 9 to both sides )

x = 9 ± 9

Then

x = 9 - 9 = 0

x = 9 + 9 = 18