Answer: x = 8 or —9
Step-by-step explanation:
x2 + x = 72
Next, bring all variables to one side of the equation:
x2 + x — 72 = 0
We find the factors of —72 such that if we add such factors together, it must result to a positive 1. These factors are — 8 and 9. Imputing these factors in the equation, we obtain:
x2 — 8x + 9x — 72 = 0
We can factorise the expression as follows
x(x — 8) + 9(x — 8) = 0x
Since the same entity appears in both brackets, we shall pick one. Doing so we have:
(x — 8)(x + 9) = 0
The values of x are calculated by the following:
x —8 = 0 or x + 9 = 0
X = 8 or x = —9
