Mathematics
protho
57

I know the answer is C. but I need to know how to solve it!

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(1) Answers
Jeuhrich

yes you are right it's C) Notice  that f(-2) = (-2)³ +2( - 2)² + 4(-2) + 8 =0 Then x³+2x²+4x+8 is divisible by (x+2) Perform this division & you will get: x³+2x²+4x+8 = (x+2)(x²+4)  The root of (x+2) is the value that render it nil, that is x=-2   The root of (x²+4) are imaginary (not real) because   x²+4 =0 ==> x² = -4 & x=√-4 or x= 2i (nor real). Hope you understood the reasoning

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