Question

ab – a – b + 1= ? 

A. (a-1)(b-1) 

B. (1-a)(1-b) 

C. (a-1)(1-b) 

D. (1-a)(b-1)

Answer 1

ab – a – b + 1 

= a(b – 1) – 1(b – 1) (taking a and – 1 as common ) 

= (a – 1)(b – 1).