Question

Find the zeros of y = x2 - 6x - 4 by completing the square.

A. x=-34/13
B. X- 3+ 118
CX13
D. x 316

Answer 1

x = 3 ±
`√(13)`

Explanation:

Given

y = x² - 6x - 4

To find the zeros let y = 0, that is

x² - 6x - 4 = 0 ( add 4 to both sides )

x² - 6x = 4

To complete the square

add ( half the coefficient of the x- term )² to both sides

x² + 2(- 3)x + 9 = 4 + 9 , that is

(x - 3)² = 13 ( take the square root of both sides )

x - 3 = ±
`√(13)` ( add 3 to both sides )

x = 3 ±
`√(13)` ← exact solutions