how to solve this equation?

Question

Solve the following equation.


(x+8)^2=2x+15

Answer 1

Hi Mike,

 

First multiply (x + 8) times (x + 8) with FOIL (multiply the first terms, outside terms, inside terms and last terms). . .

 

x^2 + 8x + 8x + 64 = x^2 + 16x + 64

 

Now set that equal to the right side of the equation. . .

 

x^2 + 16x + 64 = 2x + 15

 

Subtract 2x from each side and subtract 15 from each side. . .

 

x^2 + 14x + 49 = 0

 

Now factor with reverse FOIL. . .

 

(x + 7) (x + 7) = 0

 

So x must equal -7

 

Plug that value back into the original problem to make sure it works.

 

Have fun.

 

Dan

Answer 2

(x + 8)² = 2x + 15

(x + 8)(x + 8) = 2x + 15

x² + 16x + 64 = 2x + 15

x² + 14x + 49 = 0

(x + 7)(x + 7) = 0

 

The zero of this function is x = -7.