1.
根號(hào)下5減2倍根號(hào)6
=根號(hào)(（根號(hào)3-根號(hào)2）^2)
=根號(hào)3-根號(hào)2
2.
√xy / (y√x-x√y)
=√xy / (√xy^2-√x^2y)
= √xy /(√xy (√y-√x))
=1 / (√y-√x)
=(√y + √x) / (y - x)^2是 什么意思 ...平方 x^2 = x*x