Question

如何解方程k^3+k^2-7k-3=0

Answer 1

k^3+k^2-7k-3

=k^3+k^2-6k-k-3

=k(k^2+k-6)-(k+3)

=k(k+3)(k-2)-(k+3)

=(k+3)(k^2-2k-1)=0

k=-3或k^2-2k-1=0

即k=-3或k=1+根号2或1-根号2