Question

Solve the following quadratic equations using completing the square x2 – 8x – 34 = 0

Answer 1

4 + 5sqrt(2), 4 - 5sqrt(2)

Explanation:

x² - 8x - 34 = 0

x = [-(-8) +/- sqrt((-8)² - 4(1)(-34))]/2

x = (8 +/- sqrt200)/2

x = 4 +/- 5sqrt(2)

Answer 2

x=4± 5sqrt(2)

Explanation:

x^2 – 8x – 34 = 0

To complete the square Add 34 to each side

x^2 -8x -34+34=0+ 34

Take the coefficient of x, and divide by 2

-8/2 =-4

Then square it and add it to each side

(-4)^2 =16

x^2 – 8x +16 = 34+16

x^2 – 8x +16 = 50

We replace the left side with (x + the coefficient of x/2)^2

(x -4)^2=50

Take the square root of each side

sqrt((x -4)^2)=±sqrt(50)

x-4 = ±sqrt(25*2)

x-4 = ±sqrt(25)*sqrt(2)

x-4 = ±5sqrt(2)

Add 4 to each side

x=4± 5sqrt(2)