题型:判断题 用换元法解方程x2+2x-20x2+2x=8,若设x2+2x=y,则原方程可化为( )A.y2-8y-20=0B.8y2-20y+1=0C.y2+8y-20=0D.20y2+8y-1=0 查看答案