作业帮约分：y-x/4x^2-4y^2通分：（1）a-1/a^2-2a+1与4/a^2-1（2）2a/3b^2c,3c/5a^2b,4b/2ac^3
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约分：y-x/4x^2-4y^2通分：（1）a-1/a^2-2a+1与4/a^2-1（2）2a/3b^2c,3c/5a^2b,4b/2ac^3
约分：y-x/4x^2-4y^2
通分：（1）a-1/a^2-2a+1与4/a^2-1
（2）2a/3b^2c,3c/5a^2b,4b/2ac^3
约分：y-x/4x^2-4y^2通分：（1）a-1/a^2-2a+1与4/a^2-1（2）2a/3b^2c,3c/5a^2b,4b/2ac^3
约分:y-x/4x²-4y²=(y-x)/4(x²-y²)=(y-x)/4(x+y)(x-y)=-1/[4(x+y)]
通分:
(1) (a-1)/(a^2-2a+1)=(a-1)/(a-1)²=1/(a-1)=(a+1)/(a+1)(a-1)
4/(a^2-1)=4/(a+1)(a-1)
(2) 2a/3b^2c=20a³bc³/(30a³b³c^4)
3c/5a^2b=18a³b²c³/(30a³b³c^4)
4b/2ac^3=60a²b³c/(30a³b³c^4)
8、∵x/2=y/(-3)=z/4 -3、+3?
∴可设x/2=y/(-3)=z/4=k
则x=2k、y=-3k、z=4k
∴(x²+y²+z²)/(xy+yz+zx)
=(4k²+9k²+16k²)/(-6k²-12k²+8k²)
=-29/8
8、∵x/2=y/3=z/4
∴可设x/2=y/3=z/4=k
则x=2k、y=3k、z=4k
∴(x²+y²+z²)/(xy+yz+zx)
=(4k²+9k²+16k²)/(6k²+12k²+8k²)
=29/26
约分:＝(y-x)/4(x²-y²)=(y-x)/4(x y)(x-y)=-1/4x 4y
通分:(1)=(a-1)/(a-1)²=1/(a-1)
(2)没看懂，请标注括号后追问我2a/3*b^2*c与3c/5*a^2*b与4b/2*a*c^3 这样可以看懂吗？ 还有一题： 张老师出了这样一道题：已知x/2=y/3=z/4,求2x-y+z/3x+...
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约分:＝(y-x)/4(x²-y²)=(y-x)/4(x y)(x-y)=-1/4x 4y
通分:(1)=(a-1)/(a-1)²=1/(a-1)
(2)没看懂，请标注括号后追问我
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