Answer:
x = 18or x = - 20
Explanation:
Given
x² + 2x = 360 ( subtract 360 from both sides )
x² + 2x - 360 = 0 ← quadratic in standard form
Consider the factors of the constant term (- 360) which sum to give the coefficient of the x- term (+ 2)
The factors are + 20 and - 18, since
20 × - 18 = - 360 and 20 - 18 = 2 , thus
(x + 20)(x - 18) = 0
Equate each factor to zero and solve for x
x + 20 = 0 ⇒ x = - 20
x - 18 = 0 ⇒ x = 18
Thus the number could be 18 or - 20