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Given one factor of the polynomial, factor the polynomial completely.

16. f(x)=x^3-4x^2-7x+10;x-5

17. g(x)=2x^3+3x^2-23x-12;2x+1

1 Answer

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Use synthetic division to solve these problems

5 | 1 -4 -7 10

| v 5 5 -10

1 1 -2 0

This leads to x^2+x-2

Next we find what adds to 1 and multiplies to -2

The factors of f(x) are 2 and -1, written out as (x+2) and (x-1)

-1/2 | 2 3 -23 -12

| v -1 -1 12

2 2 -24 0

This leads to 2x^2+2x-24

Next, multiply the 2 from the a value (since a is the value with x^2 and c is the value without any x) with -24, which is -48

Now find what adds to 2 and multiplies to -48

The values for this are 8 and -6, but keep in mind, when multiplying the value of a by c, you now have to add the values in place of what you tried adding it to, this time in the problem we found using synthetic division, in this case the 2 in the b value (the middle of the equation, or the value with only one x)

2x^2+8x-6x-24

When group factoring, you'd get 2x(x+4) -6 (x+4)

So, the factors of g(x) are (x+4) and (2x-6)

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