m-n/√m-√n + m-4n - 4√mn / √m - 2√n
应该是m-n/√m-√n + m+4n - 4√mn / √m - 2√n
用+4√mn计算,不知道对不对,希望给你有些提示.
m-n/√m-√n + m+4n - 4√mn / √m - 2√n
=( √m) ^2-(√n) ^2/√m-√n + (√ m) ^2+(2√n) ^2 - 2√m√n / √m - 2√n
=(√ m-√n) ×(√ m+√n)/(√m-√n) + [ (√ m) -(2√n)] ^2 / (√m - 2√n)
=√ m+√n+√ m -2√n
=2√ m -√n
=2×√(1/3)- √(1/3) ^3
=√(1/3) ×(2-(1/√3) ^2)
=(√3/3)×(2-1/3)
=5/9 ×√3