1/4a的5次方b的2m+1次方与-1/3a的3n次方b的6次方的和依然是单项式,求m ,n(2)已知a-b=3/2,b-c=3/2,求代数式(a-c)²+3a+1-3c的值 (3)已知x-y=3xy,求2y-3xy-2x / y+2xy-x(4)若x=1/5 y=1/7,求代数式1/x+1/y除以1/x-1/y
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![1/4a的5次方b的2m+1次方与-1/3a的3n次方b的6次方的和依然是单项式,求m ,n(2)已知a-b=3/2,b-c=3/2,求代数式(a-c)²+3a+1-3c的值 (3)已知x-y=3xy,求2y-3xy-2x / y+2xy-x(4)若x=1/5 y=1/7,求代数式1/x+1/y除以1/x-1/y](/uploads/image/z/1763215-7-5.jpg?t=1%2F4a%E7%9A%845%E6%AC%A1%E6%96%B9b%E7%9A%842m%2B1%E6%AC%A1%E6%96%B9%E4%B8%8E-1%2F3a%E7%9A%843n%E6%AC%A1%E6%96%B9b%E7%9A%846%E6%AC%A1%E6%96%B9%E7%9A%84%E5%92%8C%E4%BE%9D%E7%84%B6%E6%98%AF%E5%8D%95%E9%A1%B9%E5%BC%8F%2C%E6%B1%82m+%2Cn%282%29%E5%B7%B2%E7%9F%A5a-b%3D3%2F2%2Cb-c%3D3%2F2%EF%BC%8C%E6%B1%82%E4%BB%A3%E6%95%B0%E5%BC%8F%28a-c%29%26%23178%3B%2B3a%2B1-3c%E7%9A%84%E5%80%BC+%283%29%E5%B7%B2%E7%9F%A5x-y%3D3xy%2C%E6%B1%822y-3xy-2x+%2F+y%2B2xy-x%EF%BC%884%EF%BC%89%E8%8B%A5x%3D1%2F5+y%3D1%2F7%2C%E6%B1%82%E4%BB%A3%E6%95%B0%E5%BC%8F1%2Fx%2B1%2Fy%E9%99%A4%E4%BB%A51%2Fx-1%2Fy)
1/4a的5次方b的2m+1次方与-1/3a的3n次方b的6次方的和依然是单项式,求m ,n(2)已知a-b=3/2,b-c=3/2,求代数式(a-c)²+3a+1-3c的值 (3)已知x-y=3xy,求2y-3xy-2x / y+2xy-x(4)若x=1/5 y=1/7,求代数式1/x+1/y除以1/x-1/y
1/4a的5次方b的2m+1次方与-1/3a的3n次方b的6次方的和依然是单项式,求m ,n
(2)已知a-b=3/2,b-c=3/2,求代数式(a-c)²+3a+1-3c的值
(3)已知x-y=3xy,求2y-3xy-2x / y+2xy-x
(4)若x=1/5 y=1/7,求代数式1/x+1/y除以1/x-1/y的值 (>_
1/4a的5次方b的2m+1次方与-1/3a的3n次方b的6次方的和依然是单项式,求m ,n(2)已知a-b=3/2,b-c=3/2,求代数式(a-c)²+3a+1-3c的值 (3)已知x-y=3xy,求2y-3xy-2x / y+2xy-x(4)若x=1/5 y=1/7,求代数式1/x+1/y除以1/x-1/y
1.由题意得:
2m+1=6
3n=5
即:m=5/2 n=5/3
2.由a-b=3/2,b-c=3/2得,a-b+b-c=3 即 a-c=3
那么 (a-c)²+3a+1-3c=(a-c)²+3(a-c)+1=9+9+1=19
3.2y-3xy-2x / y+2xy-x 表达不清,我认为是(2y-3xy-2x )/( y+2xy-x)
(2y-3xy-2x )/( y+2xy-x)=[-3xy-2(x-y)]/[2xy-(x-y)]
因为 x-y=3xy,上式可化为:(-3xy-6xy)/(2xy-3xy) = -9xy/(-xy)=9
4.1/x+1/y除以1/x-1/y=(y+x)/xy 除以 (y-x)/xy
= (y+x)/(y-x)
将 x=1/5 y=1/7 代入上式得:
(1/7 +1/5)/(1/7 +1/5)= -6