I understand the idea of factoring by grouping for the most part, but some of the answers in the back of the book are baffling me.

Ex) 6x3 + 9x2 - 2x2 - 3x
=(6x3 + 9x2) - (2x2 - 3x)
=3x2(2x + 3) - 1(2x + 3)
My answer: (2x + 3)(3x - 1)
Book answer: x(2x + 3)(3x - 1)

First of all, use ^ to represent powers.



Factor out an x:



Now, there is a quadratic to deal with.

What two numbers when multiplied equal -18 and when added equal 7.

How about 9 and -2.







See? What's in the parnetheses is the same. That is crucial.

According to the way you've done it, it looks like it leads into the next chapter.

how do you factor by grouping 6v^3-16v^2+21v-56?

how do you factor by grouping 6v^3-16v^2+21v-56?

Don't post your question at several places please:

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