4=3x²+x³ 怎么解

4=3x²+x³ 怎么解
4=3x²+x³ 怎么解

4=3x²+x³ 怎么解
x³+3x²-4=0
x³-x² +4x²-4=0
x²(x-1)+4(x+1)(x-1)=0
(x-1)(x²+4x+4)=0
(x-1)(x+2)²=0
∴x=1 x=-2

4=3x²+x³
x³+3x²-4=0
x³-x²+4x²-4=0
x²(x-1)+4(x²-1)=0
x²(x-1)+4(x+1)(x-1)=0
(x-1)[x²+4(x+1)]=0
(x-1)(x²+4x+4)=0
(x-1)(x+2)²=0
x-1=0或(x+2)²=0
x=1或x=-2