11. Efectuaţi:

a) 8√3a+12√3a + 3√3a-15√3a-25√3a;

9√2x+13√2x-18√2x+5√2x-10√√2. X;

b)

c) 4√5xy-7√5xy+14√5xy-9√5xy +2√5xy;

d) 5√6x²y-14√6x²y+19√6x²y-23√6x²y+8√6x²y.

(

20.