SOLUTION: When x^3+cx+d is divided by x+1, the remainder is 3, and when it is divided by x-2, the remainder is -3. Determine the values of c and d.

Algebra ->  Numeric Fractions Calculators, Lesson and Practice -> SOLUTION: When x^3+cx+d is divided by x+1, the remainder is 3, and when it is divided by x-2, the remainder is -3. Determine the values of c and d.      Log On


   



Question 177074: When x^3+cx+d is divided by x+1, the remainder is 3, and when it is divided by x-2, the remainder is -3. Determine the values of c and d.
Found 2 solutions by stanbon, solver91311:
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
When x^3+cx+d is divided by x+1, the remainder is 3
So f(-1) = -1 -c + d = 3
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and when it is divided by x-2, the remainder is -3
So f(2) = 8 + 2c + d = -3
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Determine the values of c and d.
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Rearrange to get:
-c + d = 3
2c + d = -11
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Simplify:
-2c + 2d = 6
2c + d = -11
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Add to solve for "d":
3d = -5
d = -5/3
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Substitute to solve for "c":
c = d -3
c = (-5/3) - 3
c = (-5/3) - (9/3) = -14/3
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Cheers,
Stan H.

Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!
You need to use polynomial long division to divide x%5E3+%2B+cx+%2B+d by x+%2B+1. Remember to include the missing x%5E2 term, so your dividend becomes x%5E3+%2B+0x%5E2+%2B+cx+%2B+d. Rendering polynomial long division on this site is very difficult, so I'm just going to hope you know how to do that. You will find that the remainder is d+-+%28c+%2B+1%29 which you are told is equal to 3.

Do the polynomial long division again, this time using x+-+2 as a divisor and you will discover that the remainder is d+%2B+2%28c+%2B+4%29 which you are told is equal to -3.

Now you have two 2-variable linear equations:

d+-+c+-+1+=+3 => d+-+c+=+4 and

d+%2B+2c+%2B+8+=+-3 => d+%2B+2c+=+-11

Solve this system for c and d to get your answer.