Question

Which expression represents the 4th term in the binomial expansion of (e+2f)^10

Answer 1

The answer depends on what is meant by the "fourth term". By the binomial theorem, one answer could be

$\dbinom{10}3e^3(2f)^{10-3}=120e^3(2f)^7=15360e^3f^7$

By symmetry, another could be

$\dbinom{10}3(2f)^3e^{10-3}=960e^7f^3$