Question

Solve the following quadratic by completing the square. y = x2 – 8x + 5

Answer 1

Answer:

x = 4  ± √11

Step-by-step explanation:

hello :

x²-8x+5=  x² -2(4 )(x)+5

 x²-8x+5=  x² -2(4 )(x)+5 =  ( x² -2(4 )(x) +4²) -4²+5

                                      = (x-4)²-11 .....(   completing the square )

    x²-8x+5= 0   means :      (x-4)²-11 = 0

      (x-4)²=11      but : 11 =   (√11)²  =  ( - √11)²

x-4 =√11   or    x-4 =  -√11

x = 4  ± √11                                                  

Answer 2

Answer:

x = 4 ± $\sqrt{11}$

Step-by-step explanation:

To solve the equation let y = 0 , that is

x² - 8x + 5 = 0 ( subtract 5 from both sides )

x² - 8x = - 5

To complete the square

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

x² + 2(- 4)x + 16 = - 5 + 16

(x - 4)² = 11 ( take the square root of both sides )

x - 4 = ± $\sqrt{11}$ ( add 4 to both sides )

x = 4 ± $\sqrt{11}$