√2-x=t
x=2-t²
dx=-2tdt
原式=∫(2-t²)²/t *(-2tdt)
=-2∫（4-4t²+t^4）dt
=-8t+8/3t³-2/5t^5+c
=-8√2-x+8/3(√2-x)³-2/5(√2-x)^5+c