CPM Homework Help : A2C Problem 12-181

What is the third term of $( 2 x + \frac { 1 } { 4 x } ) ^ { 7 }$ ?

Hint:

What is the third term in the expansion of $(a + b)^7$ ?

Show:

$21a^5b^2$

More Help:

Substitute $2x$ for $a$ and $\frac{1}{4x}$ for $b$ , and simplify.