a) (√2+2)²=2+4√2+4=4√2+2+4=4√2+6
b) (x-4)²=x²-2x·4+4²=x²-8x+16
c) (2-√5)(2+√5)=2²-√5²=4-5=-1
d) 1/(√2-1)=(√2+1)/(2-1)=(√2+1)/1=√2+1
e) (3-√2)/(√2+2)=(3√2-6-2+2√2)/(2-4)=(5√2-8)/-2=-(5√2-8)/2
f) (x-5)(x+5)=x²-5²=x²-25
