Question

问一道数学题,把我教会,若n^2+n-1=0,则n^3+2n^2+2002=_?(n^y就是n的y次方)

Answer 1

n^2+n-1=0

n^2+n=1

n^2=1-n

n^3+2n^2+2002

=n*(1-n)+2*(1-n)+2002

=(2+n)*(1-n)

=2-2n+n-n^2

=2-n-n^2+2002

=2-(n+n^2)+2002

因为n+n^2=1

所以2-1+2002

=1+2002

=2003