Question 43330
{{{x^2 - 7x + 12 = 0}}}
or {{{x^2 - 3x - 4x + 12 = 0}}}
or {{{x(x - 3) - 4(x - 3) = 0}}}
or (x - 3)(x - 4) = 0


As product of two quantities = 0 so at least one of them = 0.
So either (x - 4) = 0 or (x - 3) = 0 i.e. either x = 4 or x = 3.