(a+b)²=a²+2ab+b²
(a+b)(a-b)=a²-b²
a) [tex] (2+ \sqrt{5})^{2}=2²+2*2*√5+(√5)²=4+4√5+5=9+4√5
b)(√5+√6)²=(√5)²+2*√5*√6+(√6)²=5+2√30+6=11+2√30
c)(√6-√2)²=(√6)²-2*√6*√2+(√2)²=6-2√12+2=8-4√3
d)(5-√3)²=5²-2*5*√3+(√3)²=25-10√3+3=28+10√3
e)(-)( + )=(√5)²-(√3)²=5-3=2
f)( - 2)( + 2)=(√6)²-2²=6-4=2