Question

x+5分之1+x+8分之1=x+6分之1+x+7分之1

Answer 1

通分

(x+5+x+8)/(x+5)(x+8)=(x+6+x+7)/(x+6)(x+7)

(2x+13)/(x^2+13x+40)=(2x+13)/(x^2+13x+42)

(2x+13)[1/(x^2+13x+40)-1/(x^2+13x+42)]=0

因为x^2+13x+40不等于x^2+13x+42

所以1/(x^2+13x+40)-1/(x^2+13x+42)=0不成立

所以2x+13=0

x=-13/2

经检验,x=-13/2是方程的解