8. √(100-4√n)∈N
100-4√n este patrat perfect
4(25-√n) - patrat perfect⇒ (25-√n) - patrat perfect
patratele mai mici sau egale cu 25 sunt
25, 25-√n=25, n=0
16, 25-√n=16, n=81
9, 25-√n=9, n=256
4, 25-√n=4, n=441
1, 25-√n=1, n=24²=576
0, 25-√n=0, n=625
n∈{0; 81; 256, 441; 576; 625}
9. (2/√12+4/√48-3/√27)²·(9√3)=
=(1/√3+1/√3-1/√3)²·(9√3)
=(1/√3)²·(9√3)=
=1/3 · 9√3=3√3
