作业帮(a-2ab+3c)（a+2b-3c）（x+y-z）（x-y+z）2分之3a-10b×5分之10b+3a×10分之9a的平方+100的平方40又2/3×39又1/3
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(a-2ab+3c)（a+2b-3c）（x+y-z）（x-y+z）2分之3a-10b×5分之10b+3a×10分之9a的平方+100的平方40又2/3×39又1/3
(a-2ab+3c)（a+2b-3c）
（x+y-z）（x-y+z）
2分之3a-10b×5分之10b+3a×10分之9a的平方+100的平方
40又2/3×39又1/3
(a-2ab+3c)（a+2b-3c）（x+y-z）（x-y+z）2分之3a-10b×5分之10b+3a×10分之9a的平方+100的平方40又2/3×39又1/3
（x+y-z）（x-y+z）=[x+(y-z)][x-(y-z)]=x^2-(y-z)^2=x^2-y^2-z^2+2yz
40又2/3×39又1/3=(40+2/3)(40-2/3)=40^2-(2/3)^2=1600-4/9=1599又5/9
1.是否题打错了，应该是(a-2b+3c)(a+2b-3c)
(a-2b+3c)(a+2b-3c)
=[a-(2b-3c)][(a+(2b-3c)]
=a^2-(2b-3c)^2
=a^2-4b^2+12bc-9c^2
2.(x+y-z)(x-y+z)
=[x+(y-z)][x-(y-z)]
=x^2-(y-z)^2
=x^2-y^2...
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1.是否题打错了，应该是(a-2b+3c)(a+2b-3c)
(a-2b+3c)(a+2b-3c)
=[a-(2b-3c)][(a+(2b-3c)]
=a^2-(2b-3c)^2
=a^2-4b^2+12bc-9c^2
2.(x+y-z)(x-y+z)
=[x+(y-z)][x-(y-z)]
=x^2-(y-z)^2
=x^2-y^2-z^2+2yz
3.[(3a-10b)/2]）×[(10b+3a)/5]×9a^2/10+100^2
=(3a-10b)(3a+10b)/10×9a^2/10+100^2
=(9a^2-100b^2)/10×9a^2/10+100^2
=(81a^4-900a^2b^2)/100+100^2
4.40又2/3×39又1/3
=(40+2/3)(40-2/3)
=40^2-(2/3)^2
=1600-4/9
=1599又5/9
收起
(a-2ab+3c)(a+2ab-3c)
=[a-(2ab-3c)][a+(2ab-3c)]
=a^2-(4a^2b^2-12abc+9c^2)
=a^2-4a^2b^2+12abc-9c^2