x1、x2是方程x²-x-9=0的两实数根,
所以
x1+x2=1
x1²-x1-9=0
x2²-x2-9=0
x1²=x1+9
x2²=x2+9
所以
x1³+7x2²+3x2-66
=x1*(x1+9)+7(x2+9)+3x2-66
=x1²+9x1+10x2-3
=x1+9+9x1+10x2-3
=10(x1+x2)+6
=10*1+6
=16.