x1、x2为方程x2+4x+2=0的两个实数根
x1+x2=-4
x1x2=2
x1^2+4x1+2=0
x2^2+4x2+2=0
x1^3+14x2+50
=x1*(-2-4x1)+14x2+50
=-2x1-4x1^2+14x2+50
=-2x1-4(-2-4x1)+14x2+50
=-2x1+8+16x1+14x2+50
=14x1+14x2+58
=14(x1+x2)+58
=14*(-4)+58
=2