SOLUTION: (-3x cubed + y)(x squared - 8xy + 16y squared) I get as far as -3x cubed + 25x squared y + 16y cubed My book says it is -3x cubed + 25xsquared y

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Question 34484This question is from textbook Beginning and Intermediate Algebra
: (-3x cubed + y)(x squared - 8xy + 16y squared)
I get as far as -3x cubed + 25x squared y + 16y cubed
My book says it is -3x cubed + 25xsquared y - 56 xy squared + 16 y cubed
How did they find 56xy squared?
Any help would be appreciated.
Thank you, LizThis question is from textbook Beginning and Intermediate Algebra

Answer by Cintchr(475) (Show Source):
You can put this solution on YOUR website!

Alright ..... I get a very long and invoved answer here, which is not yours or the one the book gives.
First, let's work a simpler problem to see how I got this.

We multiply this out ...

Now ... lets apply this same process to the two quantities.

There are no like terms. THIS IS your answer.

SOLUTION: (-3x cubed + y)(x squared - 8xy + 16y squared) I get as far as -3x cubed + 25x squared y + 16y cubed My book says it is -3x cubed + 25xsquared y - 56 xy squared + 16 y cubed