30. Calculaţi:
a) √2-√3-√2+√3;
c) (√2+√3)² (5-2√6);
31. Rationalizati numitorul fiecăreia
b) √6-√3√2+2√3-√3√2-2√3;
d) (√2+1)(√2-1)-(√2-1)² (√2+1).