The given equation is
x^2 + 7x = 8
By subtracting 8 from both sides, it becomes
x^2 + 7x - 8 = 0
We would find two terms such that their sum or difference is 7x and the product is - 8x^2. The terms are - x and 8x. Replacing 7x with - x and 8x, we have
x^2 - x + 8x - 8 = 0
By factorising, we have
x(x - 1) + 8(x - 1) = 0
Since x - 1 is common, it becomes
(x + 8)(x - 1) = 0
x + 8 = 0 or x - 1 = 0
x = - 8 or x = 1
Option C is correct
