a³-2a²-a+7=5的解,

a³-2a²-a+7=5的解,
a³-2a²-a+7=5的解,

a³-2a²-a+7=5的解,
a³-2a²-a+7=5
a³-2a²-a+2=0
a²(a-2)-(a-2)=0
(a-2)(a+1)(a-1)=0
a1=2,a2=-1,a3=1.

a³-2a²-a+7=5
a³-2a²-a+2=0
a²(a-2)-(a-2)=0
(a-2)(a²-1)=0
(a-2)(a+1)(a-1)=0
a=2或a=-1或a=1

a^3-2a^2-a+2=0得(a-2)(a^2-1)=0得(a-2)(a+1)(a-1)=0，所以解是a=-1,a=1,a=2.