已知关于x的一元二次方程x²+2px-p²-1=0的两个实根X1,X2.若p=-1,求X1三次方+2X2²+2X2的值

p= -1时,方程x²+2px-p²-1=0可化为x²-2x-2=0
∴x1+x2=2,x1x2= -2,
(x1)³+2(x2)²+2(x2)
=(2(x1)+2)(x1)+2(x2)²+2(x2)
=2(x1)²+2(x2)²+2(x1)+2(x2)
=2(x1+x2)²-4x1x2+2(x1+x2)
=2×2²-4×(-2)+2×2
=8+8+4
=20