Question 70823
I'm not sure why you think you are stuck.  You've done everything correctly up to this point.
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All you have to do now is divide {{{4x + 12}}} by {{{x+3}}}. The answer is {{{4}}}.
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This makes the complete answer to your problem {{{x^2 - x + 4}}}. To check this answer,
multiply it by {{{x+3}}} and see if you don't get back to the original dividend of {{{x^3+2x^2+x+12}}}.
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You seem to understand the division process.  Good work!