SOLUTION: Given the identity Ax^3+x^2-2x-3=(3x+B)(x-1)(x+2)+C(x-1)+D , find the values of the constants A,B,C and D. Hence or otherwise, find the remainder when Ax^3+x^2-2x-3 is divided by x

Algebra ->  Test -> SOLUTION: Given the identity Ax^3+x^2-2x-3=(3x+B)(x-1)(x+2)+C(x-1)+D , find the values of the constants A,B,C and D. Hence or otherwise, find the remainder when Ax^3+x^2-2x-3 is divided by x      Log On


   



Question 696139: Given the identity Ax^3+x^2-2x-3=(3x+B)(x-1)(x+2)+C(x-1)+D , find the values of the constants A,B,C and D. Hence or otherwise, find the remainder when Ax^3+x^2-2x-3 is divided by x–1.
Answer by MathTherapy(10555) About Me  (Show Source):
You can put this solution on YOUR website!
Given the identity Ax^3+x^2-2x-3=(3x+B)(x-1)(x+2)+C(x-1)+D , find the values of the constants A,B,C and D. Hence or otherwise, find the remainder when Ax^3+x^2-2x-3 is divided by x–1.

%283x+%2B+B%29%28x+-+1%29%28x+%2B+2%29+%2B+C%28x+-+1%29+%2B+D+=+Ax%5E3+%2B+x%5E2+-+2x+-+3
%283x+%2B+B%29%28x%5E2+%2B+x+-+2%29+%2B+C%28x+-+1%29+%2B+D+=+Ax%5E3+%2B+x%5E2+-+2x+-+3
3x%5E3+%2B+3x%5E2+-+6x+%2B+Bx%5E2+%2B+Bx+-+2B+%2B+Cx+-+C+%2B+D+=+Ax%5E3+%2B+x%5E2+-+2x+-+3
3x%5E3+%2B+3x%5E2+%2B+Bx%5E2+-+6x+%2B+Bx+%2B+Cx+-+2B+-+C+%2B+D+=+Ax%5E3+%2B+x%5E2+-+2x+-+3 ----- Rearranging terms


From the above, we can see that:
3x%5E3+=+Ax%5E3 -------- highlight_green%283+=+A%29

3x%5E2+%2B+Bx%5E2+=+x%5E2 ------ Bx%5E2+=+x%5E2+-+3x%5E2 ------ Bx%5E2+=+-+2x%5E2 ----- highlight_green%28B+=+-+2%29

-+6x+%2B+Bx+%2B+Cx+=+-+2x ----- x%28-+6+%2B+B+%2B+C%29+=+x%28-+2%29 ---- -+6+%2B+B+%2B+C+=+-+2 ----- B+%2B+C+=+4
-+2+%2B+C+=+4 ----- Substituting – 2 for B
C = 4 + 2, or highlight_green%28C+=+6%29

-+2B+-+C+%2B+D+=+-+3
-+2%28-+2%29+-+6+%2B+D+=+-+3 ----- Substituting – 2 for B, and 6 for C
4+-+6+%2B+D+=+-+3
D = - 3 + 2, or highlight_green%28D+=+-+1%29


With A+=+3, Ax%5E3+%2B+x%5E2+-+2x+-+3 becomes: 3x%5E3+%2B+x%5E2+-+2x+-+3, and when divided by x – 1, we have a remainder, or f(1) = 3%281%29%5E3+%2B+%281%29%5E2+-+2%281%29+-+3, or 3+%2B+1+-+2+-+3, or highlight_green%28-+1%29

You can do the check!!

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