已知x=根号2-1,则根号（x³+2x²-x+8﹚=?求大神,求详细过程,

已知x=根号2-1,则根号（x³+2x²-x+8﹚=?求大神,求详细过程,
已知x=根号2-1,则根号（x³+2x²-x+8﹚=?
求大神,求详细过程,

已知x=根号2-1,则根号（x³+2x²-x+8﹚=?求大神,求详细过程,
原式=√x³+2x²+x-2x+8
=√x（x²+2x+1）-2x+8
=√x（√2-1+1）²-2x+8
=√2x-2x+8
=2√2