Question

How do you multiply `(3x - y ) \cdot ( 9x ^ { 2} + y ^ { 2} ) \cdot ( 3x + y )`?

Answer 1

`81x^4-y^4`

Explanation:

Writing your product in the form
`(3x-y)(3x+y)(9x^2+y^2)=(9x^2-y^2)(9x^2+y^2)=`
`81x^4-y^4`
after the Formula
`a^2-b^2=(a-b)(a+b)`