Question

n的平方加上n减1等于0 求n的立方加上n的平方的二倍加上2009等于?

Answer 1

因：n^2+n-1=0

所以：n^2+n=1

n^3+2n^2+2009

=n(n^2+n)+n^2+2009

=n*1+n^2+2009

=n+n^2+2009

=1+2009

=2010