若1/a:1/b:1/c=2:3:4,则a:b:c帮我看一下..1.若1/a:1/b:1/c=2:3:4,则a:b:c=1/2:1/3:1/42.(a^-3乘b^4)^3乘(3a^2乘b)^-23.1/x+1/2x+1/3x=3/x4.12/(a^2-9)+2/(3-a)=-2/(a-3)5.若方程2/(x-2)+mx/(x^2-4)=3/(x+2)有增根,则m的值=

Question

若1/a:1/b:1/c=2:3:4,则a:b:c
帮我看一下..
1.若1/a :1/b :1/c=2:3:4,则a:b:c=1/2 :1/3 :1/4
2.(a^-3乘b^4)^3 乘 (3a^2乘b)^-2
3.1/x + 1/2x + 1/3x=3/x
4.12/(a^2-9) + 2/(3-a)=-2/(a-3)
5.若方程2/(x-2) + mx/(x^2-4)=3/(x+2)有增根,则m的值=

Answer 1

1.若1/a :1/b :1/c=2:3:4,则a:b:c=1/2 :1/3 :1/4
对
2.(a^-3乘b^4)^3 乘 (3a^2乘b)^-2
=3^-2*a^-13*b^10
3.1/x + 1/2x + 1/3x=3/x
1/x + 1/2x + 1/3x=6/6x+3/6x+2/6x=11/6x
错误
4.12/(a^2-9) + 2/(3-a)=-2/(a-3)
12/(a^2-9) + 2/(3-a)
=12/(a^2-9)-2/(a-3)
=12(a+3)(a-3)-6(a+3)/(a+3)(a-3)
=(12-6a-18)/(a+3)(a-3)
=-(6a+6)/(a+3)(a-3)
错误
5.若方程2/(x-2) + mx/(x^2-4)=3/(x+2)有增根,则m的值=
两边乘(x+2)(x-2)
2(x+2)+mx=3(x-2)
增根则公分母为0
x=2,x=-2
x=2,则2*4+2m=0,m=-4
x=-2,则0-2m=3*(-4),m=6
所以m=-4,m=6