Q.

Expand (x2+3x)4,  x≠0.

1 x8+12x5+54x2+108x+81x4  
2 x8-12x5+54x2-108x-81x4  
3 x8-12x5-54x2+108x+81x4  
4 None of these  

Ans.

(1)

We have,

(x2+3x)4=C04(x2)4+C14(x2)3(3x)+C24(x2)2(3x)2+C34(x2)(3x)3+C44(3x)4

=x8+4x6·3x+6x4·9x2+4x2·27x3+81x4

=x8+12x5+54x2+108x+81x4