Find all the roots of x^3+x^2-36x+42 divided by x+7 using long division

Answer 1

-7 | 1 1 -36 42

-7 42 -42

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1 -6 6 0

So you want the roots of

x^2 - 6x + 6 = 0

[6 +or- sqrt ( 36 - 4*6 )] / 2

[6 +or- sqrt(12)] / 2

[ 6 +or- 2*sqrt(3)]/2

3 +or- sqrt(3)