Answer:
B. 4375x^4
Explanation:
Firstly, you can just multiply it and look at the fourth term or use the binomial theorem. Either way it's B.
4375x^4.
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.
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