Question 27566
4r^2 + 6rs + 9s^2

           2r -3s
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       -12r^2s    -18rs^2   -27s^3
8r^3   + 12r^2s   + 18rs^2
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8r^3 - 27s^3


Multiply all terms on the top line by all terms on the second line.
Then, add all like terms.
I hope that is right.