Question

( begin{aligned} & operatorname{sel}(12)(x+1)^{3}+(x-1)^{3} &=x^{3}+1^{3}+3 x cdot 1(x+1)+x^{3}-1^{3}-3 x cdot 1(x-1) =& x^{3}+1+3 x^{2}+3 x+x^{3}-1-3 x^{2}+3 x =& 2 x^{3}+6 x =& 2 xleft(x^{2}+3right) text { Ans. } end{aligned} )
( Rightarrow ) of forn is correct.

# 42. (x + 1)2 + (x - 1)3 is equal to (1) 2x(x2 + 3) (2) (x² + 3) (3) (x2 + 2x + 1) (4) (x + 1)(x2 + 3)

Solution