Question 201759
( x^2 -3x -4) / (x^2-16) / (3x+3) / (x^2 +9x+20)
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{ (x^2 -3x-4) / (x^2 -16)} * {  (x^2 +9x +20)/ (3x+3) } ,,,invert  and  multiply
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factor
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{ (x+1)(x-4) / (x+4)(x-4) } * { (x+5)(x+4) / 3 (x+1) }
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simply  by  canceling  like  terms
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(x+5) / 3
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check,  let  x=0,, original  and  answer = 5/3,,,ok