<PRE><B>Question 536968</B>
(z-4)/(z-8)-(z+1)/(z+8)+(z-72)/(z^2-64)
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least common denominator: z^2-64
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Rewrite each term with the lcd as its denominator:
[(z-4)(z+8)]/lcd - [(z+1)(Z-8)]/lcd + [(z-72)]/lcd
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Combine the numerators over the lcd:
[z^2+4z-32 - [z^2-7z-8] + z-72]/lcd
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[z^2+4z-32-z^2+7z+8+z-72]/lcd
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= [12z-96]/[z^2-64]
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= [12(z-8)]/[z^2-64]
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= 12/(z+8]
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Cheers,
Stan H. </PRE>