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So the question is

Find a polynomial f(x) of degree 5 such that both of these properties hold:

 f(x) is divisible by x^3

f(x)+2  is divisible by (x+1)^3

 

I understand the problem and I know you have make a system of equations solving for a, b, and c because the function will be in the form\

a^5+b^4+c^3. I also found -a+b-c=-2 but I cant find the other two equations. 

Can you help?

 Jan 21, 2021
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Since f(x) is divisible by x^3, f(x) is of the form ax^5 + bx^4 + cx^3.

 

You then want ax^5 + bx^4 + cx^3 + 2 to be divisible by (x + 1)^3.  Using long division, you get the equations

-10a  + 6b - 3c = 0

4a - 3b + 2c = 0

-a + b - c + 2 = 0

==> a = 6, b = 16, c = 12

 

So f(x) = 6x^5 + 16x^4 + 12x^3.

 Jan 23, 2021

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