Question

What is the fifth term of (x-2y)^7

Answer 1

560x^3y^4.

Explanation:

The (r+1)th term of (a + b)^r = nCr a^(n-r) b^r

We want the fifth term so r = 5 - 1 = 4:

(4 + 1)th term = 7C4 x^(7-4) (-2y)^4

= 35x^3 16y^4

= 560x^3y^4.