1.(b/√a)÷(√ab)*(1/√ab)
=b/√a*(1/√ab)*(1/√ab)
=b/√a*1/ab
=1/a*√a
=√a/a²
2.√X=2
(√X)²=2²
X=4
3.[√(2x-1)]²=4 (如果是√（2X-1）²也是一样的）
2X-1=4(当x>1/2)
X=5/2
4.X²+(X²-1)/X÷[X-(2X-1/x)]
=X²+(X²-1)/X*1/[X-(2X-1/x)]
=X²+(X²-1)/X*1/[(X²-2X+1)/x]
=X²+(X²-1)/X*X/[(X²-2X+1)]
=X²+(X+1)(X-1)*1/[(X+2)(X-1)]
=X²+(X+1)/(X+2)
当X=√2+1时
带入即得.