（2011•邢台一模）已知x=22，求(3xx−1−xx+1)•x2−1x+2的值．

Question

（2011•邢台一模）已知x=(√(2))/(2)，求((3x)/(x−1)−(x)/(x+1))•(x2−1)/(x+2)的值．

Answer 1

当x=(√(2))/(2)时，
原式=[(3x(x+1)−x(x−1))/((x−1)(x+1))]•((x+1)(x−1))/(x+2)，
=(2x(x+2))/((x+1)(x−1))•((x+1)(x−1))/(x+2)，
=2x，
=2×(√(2))/(2)，
=√(2)．