(1988+1989*1987)/(1988*1989-1)＝？

=(1989-1+1989*1987)/(1988*1989-1)
=(1989*1988-1)/(1988*1989-1)

原式=（1989-1+1987*1989）/(1988*1989-1)
=（1988*1989-1）/(1988*1989-1)
=1

他988加1989乘1987分之1988，算起来是0加1=1

1

[a+(a+1)*(a-1)]/[a*(a+1)-1]

(1988+1989*1987)/(1988*1989-1)
=(1988+(1988+1)*(1988-1))/(1988*(1988+1)-1)
=(1988^2+1987)/(1988^2+1987)
=1
或者
javascript:alert((1988+1989*1987)/(1988*1989-1))
电脑就给你算出来了