2(5x×2x+5×5x+2x×5)=40怎么算的,

问题描述:

2(5x×2x+5×5x+2x×5)=40怎么算的,

2(5x×2x+5×5x+2x×5)=40
10x^2+25x+10x=20
2x^2+7x-4=0
(2x-1)(x+4)=0
x=1/2或x=-4