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.
Answer:
x=7 or x=-3
Step-by-step 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
