(40-x)(60+x/5*30)=3600

问题描述:

(40-x)(60+x/5*30)=3600
解答

(40-x)(60+6x)=3600
两边除以-6
(x+10)(x-40)=-600
x²-30x+200=0
(x-10)(x-20)=0
x=10,x=20