(30+20x)(49-x)=2100

问题描述:

(30+20x)(49-x)=2100

-10(2x+3)(x-49)=2100
(2x²-95x-147)=-210
2x²-95x+63=0
判别式 = (-95)²-4×2×63 = 9025-504 = 8521
跟 = (95±√8521)/4