Question

若n²+3n=1,求n(n+1)(n+2)+1的值.

Answer 1

n²+3n=1

n=(-3±√5)/2

n(n+1)(n+2)+1

=n³+3n²+2n+1

=n(n²+3n)+2n+1

=3n+1

=3(-3±√5)/2+1

=(-7±3√5)/2