factorization

8(7x+5y)^3-125(3x+2y)^3
=(14x+10y)^3-(15x+10y)^3
THEN USE a^3-b^3=(a-b)(a^2+ab+b^2)
=(14x+10y-15x-10y)[(14x-10y)^2+(14x+10y)(15x+10y)+(15x+10y)^2]
THE REST CALCULATE BY YOURSELF

2007-09-09 19:06:12 補充：
不懂可以問我

2007-09-09 19:10:48 補充：
THE FOLLOWING ANSWER IS WRONG!IT SHOULD BE=(14x十10y-15x-10y)[(14x十10y)^2 (14x十10y)(15x 10y)十(15x十10y)^2]=-x(196x^2十280xy十100y^2十210x^2十290xy十100y^2十225x^2十300xy十100y^2)=-x(631x^2十570xy十300y^2).....

2007-09-09 19:12:38 補充：
IT IS FACTORIZATION, NOT EXPANSION!!

2007-09-09 19:15:21 補充：
=-x(631x^2十870xy十300y^2)

8(7x+5y)^3-125(3x+2y)^3
=[2(7x+5y)]^3-[5(3x+2y)]^3
=(14x+10y)^3-(15x+10y)^3
=(14x+10y-15x-10y)[(14x+10y)^2+(14x+10y)(15x+10y)+(15x+10y)^2]
= -(196x^2+280xy+100y^2+210x^2+290xy+100y^2+225x^2+300xy+100y^2)
= -(631x^2+1066xy+200y^2)
= -631x^2-1066xy-200y^2

2007-09-09 19:08:08 補充：
利用（a^3-b^3）=(a-b)(a^2 ab b^2)公式計算。

2007-09-09 19:08:48 補充：
利用（a^3-b^3）=(a-b)(a^2+ab+b^2)公式計算。