Question 74683
{{{(2r-3s)(4r^2+6rs+9s^2)}}}
{{{8r^3+12r^2s+18rs^2-12r^2s-18rs^2-27s^3}}}Multiply
{{{8r^3+cross(12r^2s-12r^2s)+cross(18rs^2-18rs^2)-27s^3}}}Notice these terms cancel to zero. So you're left with
{{{8r^3-27s^3}}}This is the simplified form.
You had the right answer at first. However, I don't know where you got {{{48r^4-162s^4}}}