Question

Factorize each of the following expression:
ab − a − b + 1

Answer 1

$$\begin{gathered} ab-a-b+1=(ab-b)+(1-a)[Regroupingtheexpressions] \\ =b(a-1)+(1-a) \\ =b(a-1)-(a-1)[\because (1-a)=-(a-1\left)\right] \\ =(a-1)(b-1)[Takingoutthecommonfactor(a-1\left)\right] \end{gathered}$$