Question

Solve the equation by completing the square. x^2 -2x = 15

Answer 1

Answer:

x = -3  or  x = 5

Step-by-step explanation:

Solve:   x^2 -2x = 15

x^2  - 2x  - 15 = 0

Use the Diamond method of factoring

-15 = 3* -5  and  3 - 5 = -2  so...

x^2  - 2x  - 15 = x^2 -  5x  + 3x  -  15

x^2  - 2x  - 15 = x *(x - 5)  + 3*(x - 5)

x^2  - 2x  - 15 = (x  + 3)*(x - 5)

x^2  - 2x  - 15 = (x  + 3)*(x - 5)  = 0

solve  (x + 3 ) = 0  and  (x - 5) = 0

x = -3  or  x = 5