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find the product of (3x-5y-4)(9x^2+25y^2+15xy+12x-20y+16) .

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best_answer

solution: we have , 

                (3x-5y-4)(9x^2+25y^2+15xy+12x-20y+16)

               =   left  3x+(-5y)+(-4) 
ight \left  (3x)^2+(-5y)^2+(-4)^2-(3x)(-5y)-(-5y)(-4)-3x(-4)
ight

                =   (a+b+c)(a^2+b^2+c^2-ab-bc-ca)  , where a=3x ,b=-5y ,c=-4

                    =a^3+b^3+c^3-3abc 

                  =(3x)^3+(-5y)^3+(-4)^3-3(3x)(-5y)(-4)=27x^3-125y^3-180xy-64 

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Deependra Verma

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