二道七年级数学题?

1运用简便方法计算:75*2.6^2-12*3.5^2
75*2.6^2-12*3.5^2
=3[25*2.6^2-4*3.5^2]
=3[(5*2.6+2*3.5)(5*2.6-2*3.5)]
=3*(13+7)(13-7)
=3*20*6
=360

2因是分解:32(x-y)+8(y-x)^3
32(x-y)+8(y-x)^3
=8[4(x-y)-(x-y)^3]
=8[(x-y)(4-(x-y)^2)]
=8(x-y)(2+x-y)(2-x+y)

75*2.6^2-12*3.5^2=3*(5*2.6)^2-3*(2*3.5)^2=3*(13+7)(13-7)=360

32(x-y)+8(y-x)^3=8(y-x)[(y-x)^2-4]=8(y-x)(y-x+2)(y-x-2)