a,b是方程x^2-x-1=0的两个实数根,
所以a^2-a-1=0
b^2-b-1=0
所以a^2=a+1,b^2=b+1
ab=-1
a^2+a(b^2-2)
=a+1+a(b+1-2)
=a+1+ab-a
=ab+1
=-1+1
=0