.已知 1/a-1/b=1,求分式(2a+3ab-2b)/(a-2ab-b)的值 2.已知x/3=y/2=z/5,求分式(xy+yz+zx)/(x^2+y^2+z^2)的值 3.小惠坐在匀速行驶的公交车上,注意到路边间隔均匀的排着一些广告牌.他利用手表看1分钟内车窗掠过
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![.已知 1/a-1/b=1,求分式(2a+3ab-2b)/(a-2ab-b)的值 2.已知x/3=y/2=z/5,求分式(xy+yz+zx)/(x^2+y^2+z^2)的值 3.小惠坐在匀速行驶的公交车上,注意到路边间隔均匀的排着一些广告牌.他利用手表看1分钟内车窗掠过](/uploads/image/z/3932930-2-0.jpg?t=.%E5%B7%B2%E7%9F%A5+1%2Fa-1%2Fb%3D1%2C%E6%B1%82%E5%88%86%E5%BC%8F%282a%2B3ab-2b%29%2F%28a-2ab-b%29%E7%9A%84%E5%80%BC+2.%E5%B7%B2%E7%9F%A5x%2F3%3Dy%2F2%3Dz%2F5%2C%E6%B1%82%E5%88%86%E5%BC%8F%28xy%2Byz%2Bzx%29%2F%28x%5E2%2By%5E2%2Bz%5E2%29%E7%9A%84%E5%80%BC+3.%E5%B0%8F%E6%83%A0%E5%9D%90%E5%9C%A8%E5%8C%80%E9%80%9F%E8%A1%8C%E9%A9%B6%E7%9A%84%E5%85%AC%E4%BA%A4%E8%BD%A6%E4%B8%8A%2C%E6%B3%A8%E6%84%8F%E5%88%B0%E8%B7%AF%E8%BE%B9%E9%97%B4%E9%9A%94%E5%9D%87%E5%8C%80%E7%9A%84%E6%8E%92%E7%9D%80%E4%B8%80%E4%BA%9B%E5%B9%BF%E5%91%8A%E7%89%8C.%E4%BB%96%E5%88%A9%E7%94%A8%E6%89%8B%E8%A1%A8%E7%9C%8B1%E5%88%86%E9%92%9F%E5%86%85%E8%BD%A6%E7%AA%97%E6%8E%A0%E8%BF%87)
.已知 1/a-1/b=1,求分式(2a+3ab-2b)/(a-2ab-b)的值 2.已知x/3=y/2=z/5,求分式(xy+yz+zx)/(x^2+y^2+z^2)的值 3.小惠坐在匀速行驶的公交车上,注意到路边间隔均匀的排着一些广告牌.他利用手表看1分钟内车窗掠过
.已知 1/a-1/b=1,求分式(2a+3ab-2b)/(a-2ab-b)的值
2.已知x/3=y/2=z/5,求分式(xy+yz+zx)/(x^2+y^2+z^2)的值
3.小惠坐在匀速行驶的公交车上,注意到路边间隔均匀的排着一些广告牌.他利用手表看1分钟内车窗掠过几个广告牌.他开始看表和结束看表都是在某2个牌子的正中央,而且把1分钟内掠过的广告牌数目乘以k,正好等于该汽车每小时开的千米数,请计算出2个广告牌之间的距离(用含k的代数式表示)
.已知 1/a-1/b=1,求分式(2a+3ab-2b)/(a-2ab-b)的值 2.已知x/3=y/2=z/5,求分式(xy+yz+zx)/(x^2+y^2+z^2)的值 3.小惠坐在匀速行驶的公交车上,注意到路边间隔均匀的排着一些广告牌.他利用手表看1分钟内车窗掠过
1.1/a-1/b=1
(b-a)/(ab)=1
ab=b-a
(2a+3ab-2b)/(a-2ab-b)
=[2a+3(b-a)-2b]/[a-2(b-a)-b]
=(b-a)/(3a-3b)
=-1/3
2.令x/3=y/2=z/5=k,
x=3k,y=2k,z=5k.
(xy+yz+zx)/(x^2+y^2+z^2)
=(6k^2+10k^2+15k^2)/(9k^2+4k^2+25k^2)
=31/38
3.设有X个广告牌.则有X个2个广告牌之间的距离.
该汽车每分钟开的千米数=X*K/60
2个广告牌之间的距离=(XK/60)/X=K/60
1、由1/a-1/b=1得(b-a)/ab=1即ab=b-a
原式={2a+3(b-a)-2b}/{a-2(b-a)-b
=(b-a)/3(a-b)=-1/3