Question

Which expression represents the fourth term in the binomial expansion of (e + 2f)10?

Answer 1

Answer:

A: 10C3(e7)(2f)3

Step-by-step explanation:

Answer 2

The fourth term of the binomial expansion $(e+2f)^{10}$ can be calculated using the formula for (i+1)-th term of the binomial expansion:

$T_{i+1}=C_{10}^i\cdot e^{10-i}\cdot (2f)^i.$

In order to find term $T_4$, determine that

$i+1=4\Rightarrow i=3.$

Now

$T_4=C_{10}^3\cdot e^{10-3}\cdot (2f)^3=C_{10}^3\cdot e^7\cdot (2f)^3.$

Answer: correct choice is A