ps 500 test21 #11

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ps 500 test21 #11

by dunkin77 » Sun Apr 08, 2007 12:18 pm
Hi,

For some reason, when I calcurate the answer is -4.... but the answer should be A) - can anyone please help?
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by sapnalakhi » Sun Apr 08, 2007 1:03 pm
The above expression can be simplified as:

Taking LCM:

Denominator would be (z-3)(z-1)

so (z-3)(z+3) + (z+1)(z-1) / (z-3)(z-1) = 2

z^2-9 + z^2 - 1 = 2 (z-3)(z-1)

2z^2 - 10 = 2(z^2 - 4z + 3)

2z^2 - 10 = 2z^2 - 8z + 6

Cancel 2z^2 on both sides

so, 8z = 16

and z= 2.

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by Cybermusings » Tue Apr 10, 2007 2:50 am
(z+3/z-1) + (z+1/z-3) = 2
{[(z+3)*(z-3)] + [(z+1)*(z-1)]} / (z-1)(z-3) = 2
z^2 - 9 + z^2 - 1 = 2 {z^2 - 3z - z + 3}
(z^2 - 5) = z^2 - 4z + 3
-4z = -8
Thus z = 2

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by RAGS » Tue Apr 10, 2007 11:19 am
Why would any one want to take LCM or simplify the prob
when all u need to do is plug in the given ans and check