$\"\"$

Binomial theorem:

Let $\"\"$ and $\"\"$ be a real numbers.For any positive integer $\"\"$ ,

$\"\"$

The expression is $\"\"$ .

By using binomial theorem,

$\"\"$

In the above expansion, the fifth term has the coefficient of $\"\"$ .

The coefficient of $\"\"$ .

$\"\"$

The coefficient of $\"\"$ is $\"\"$ .