用换元法解下列方程:(1) x^4-3x^2-4=0 (2) (2y+1)^2+3(2y+1)+2=0
问题描述:
用换元法解下列方程:(1) x^4-3x^2-4=0 (2) (2y+1)^2+3(2y+1)+2=0
答
frgregtr
答
(1)设x^2=t,则t^2-3t-4=0 t=4或-3(-3舍去) 那么x^2=4,x=±2
(2)设2y+1=t,则t^2+3t+2=0 t=-2或-1 当t=-2时,y=-3/2 当t=-1时,y=-1