Answers

2014-08-01T19:25:33+08:00
X²-x-12/16-x²
=  (x-4)(x+3)/(4-x)(4+x)      /  multiply both the numerator
                                             denomerator by -1
 =  -1(x-4)(x+3)/-(4-x)(4+x)
 =  - (x-4)(x+3)/(x-4)(4+x)        / cancelled (x-4)
 =    - (x+3)/(4+x)
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