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# [Core 4] Rational Fractions Watch

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1. Here is the question:

I did
A(x+1)(x+5) + B(x-1)(x+5) + C(x-1)(x+1) = 3x2 + 28x + 17

Then to work out each constant:

A: let x = 1
12A = 3 + 28 + 17 => A = 4

B: let x = -1
-8B = 3 - 28 + 17 => B = 4

C: let x = -5
24C = 192 - 140 + 17 => C = 2.875

However when I add my three fractional components on WolframAlpha, I do not get the same answer as I what I am trying to express.

Help would be appreciated, thanks.
2. Mistake on B and C,

-8B = 3-28+17

-8B = -8

so B=....

and For C, 3(-5)^2 = 75 not 192
3. (Original post by NotNotBatman)
Mistake on B and C,

-8B = 3-28+17

-8B = -8

so B=....

and For C, 3(-5)^2 = 75 not 192
Damn.. My mistakes were so stupid. I got B = 1 and C = - 2, is this correct?
4. (Original post by DarkEnergy)
Damn.. My mistakes were so stupid. I got B = 1 and C = - 2, is this correct?
Yes, that's correct.
5. (Original post by NotNotBatman)
Yes, that's correct.

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Updated: October 4, 2016
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