Question

当x=-1/2时代数式x/(x+1)-(x+3)/(x+1).（2x^2+6x)/(x^2+6x+9)的值恰好是分式方程

Answer 1

x/(x+1)-(x+3)/(x+1)*（2x^2+6x)/(x^2+6x+9)的

=x/(x+1)-(x+3)/(x+1)*2x(x+3)/(x+3)^2

=x/(x+1)-2x/(x+1)

=-x/(x+1)

x=-1/2

原式=（1/2）/(1/2)=1

1是分式方程2/(x-2)+mx/(x^2-4)=0的根

代入

2/(1-2)+m/(1-4)=0

m=-6

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