$\"\"$

The expression is $\"\"$ .

Compare the binomial expression $\"\"$

Then write $\"\"$ .

The formula for coefficient of x^j in the expression of $\"\"$ is $\"\"$ .

The coefficient of x³ in the expression of $\"\"$ is $\"\"$ .

$\"\"$

$\"\"$ $\"\"$

$\"\"$ $\"\"$ .