Task/25565246
----------
1.
a/√(a² +ab) - √a/√(a +b) = a/√(a(a +b)) - √a *√a /√(a +b) *√a =
a/√(a(a +b)) - a /√a(a +b ) = 0 .
---
2.
2/(√p -√q) -2(√p) / (p -q) =2(√p +√q -√p ) /(p-q) =2(√q)/ (p -q) =
|| p=9,q =8|| = 2(√9) /(8 -9) =2*3 /(-1) = - 6.
---
3.
(a - 81b)/ (√a -9√b) = ((√a)² -(9√b)² )/ (√a -9√b) =
(√a -9√b) (√a +9√b)/ (√a -9√b) = √a +9√b.
---
4.
(a+27b)/ (∛a +3∛b) =((∛a)³ +(3∛b)³) / (∛a +3∛b) =
(∛a +3∛b)( ∛a² - 3∛(ab) +9∛b² ) / (∛a +3∛b) = ∛a² - 3∛(ab) +9∛b² .
* * * * a³ +b³ =(a+b)(a² -ab +b²) * * *
-------------
Удачи !