a)
[tex]x=\frac{3\sqrt{3}*5\sqrt{5}}{8\sqrt{15}}=\frac{15\sqrt{15}}{8\sqrt{15}}=15/8[/tex]
b)
[tex]\frac{-2\sqrt{3} }{3\sqrt{2} } =Amplificam~cu~radical~din~2=\frac{-2\sqrt{3}*\sqrt{2} }{3\sqrt{2} *\sqrt{2} }=\frac{-2\sqrt{6} }{3*2} =\frac{-\sqrt{6} }{3}[/tex]
c)
a=(1-√2)²+(√2+1)²-2(√2-1)(√2+1)
a=1-2√2+2+2+2√2+1-2(2-1)
a=1-2√2+2+2+2√2+1-2
a=1+2+2+1-2
a=4
√a=√4=2∈N
