Question

Let a and b be the coefficient of x to the power 3 in (1+x+2x square+3x cube)to the power 4 and (1+x+2x square+3x cube+4xto the power 4)to the power 4 respectively. Then the value of 4a/b is :

Answer 1

Step-by-step explanation:

We have b= coefficient of x3 in

((1+x+2x2+3x3)+4x4)4

= coefficient of x3 in [4C0(1+x+2x2+3x3)4(4x4)0+ 4C1(1+x+2x2+3x3)3(4x4)1+...]

= coefficient of x3 in (1+x+2x2+3x3)4=

Hence, 

.

.

4a/b=4.