Question

36+4x=x^2+15
What is x?

Answer 1

x=7 or x=-3

Explanation:

36+4x=x^2+15

36-15+4x=x^2

21+4x=x^2

0=x^2-4x-21

0=x^2-(7-3)x-21

0= x^2-7x+3x-21

0= x(x-7)+3(x-7)

0= (x-7)(x+3)

so either

x-7=0

x=7

or x+3=0

x=-3

Answer 2

X = -3 or X = 7

Step 1: Simplify both sides of the equation.

Step 2: Subtract x^2+15 from both sides.

Step 3: Factor left side of equation.

Step 4: Set factors equal to 0.