Question

The second, third and fourth terms in the binomial expansion (x + a)

n

are 240, 720 and 1080,

respectively. Find x, a and n.

Answer 1

In this question, we will use the concept of binomial expansion and the concept of combination.

We should take note that the the first term of a binomial expansion is 0.

We begin counting from 0 and not 1.

For instance the second term is
(x + a) ¹

The third term :
(x + a) ²

Fourth term:
(x + a) ³

With this information we can do the calculations.

When we calculate this we get :

a = 3, x = 2 and n=5.

Find working in the images.