5.

((x^2-2x-15)/(x^2-4x-21))((2x^2-6x-56)/(2x^2-2x-40))

 

Factor. First factor out the common factor in the top and bottom of the second fraction.

 

((x^2-2x-15)/(x^2-4x-21))(2(x^2-3x-28))/(2(x^2-x-20))

 

Next factor the quadratics.

((x+3)(x-5))/((3+3)(x-7))(2(x-7)(x+4))/(2(x-5)(x+4))

 

 

Everything cancels out and we are left with an answer of

 

 

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