Find the 4th term of (x+5) ^7

A. 35x^4

B. 4375x^4

C. 21,875x^3

D. 625x^4

4375x^4.

Step-by-step explanation:

There is a useful formula for answering these type of questions. It is:

(r + 1) th term of (x + a) ^n = nCr x^ (n-r) a^r.

4th term = (3 + 1) th term of (x + 5) ^7

= 7C3 x^ (7-3) 5^3

= 35 x^4 * 125

= 4375x^4.

B. 4375x^4

Step-by-step explanation:

Firstly, you can just multiply it and look at the fourth term or use the binomial theorem. Either way it's B.