x乘(x+1)乘(x+2)乘(x+3)等于360
x(x+1)(x+2)(x+3)=360
x(x+3)(x+1)(x+2)=360
(x²+3x)(x²+3x+2)=360 令y=x²+3x+1
(y-1)(y+1)=360
y²-1=360
y²=361
y=±√361=±19
x²+3x+1=±19
1）
x²+3x+1=19
x²+3x-18=0
(x+6)(x-3)=0
x1=-6
x2=3
2)
x²+3x+1=-19
x²+3x+20=0
△=3²-4X20=9-80=-71
無實數(shù)解
x3=(-3+√71i)/6
x4=(-3-√71i)/6