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Verified answer

104(1)
((1/(√13-√17)+1/(√17+√13))*√13=(√17+√13+√13-√17)/(13-17)*√13=
=2√13/(-4)*√13=-13/2=-6,5
104(2)
((5/(√6+11)+5/(√6-11))*0<1*√6=5(√6-11+√6+11)/(6-121)*0,1*√6=
=5*2√6/(-115)*√6/10=-10√6/115*√6/10=-6/115
104(3)1/(8-√28)+1/(8+√28)=(8+√28+8-√28)/(64-28)=16/36=4/9
104(4)
1/(6+4√2)+1/(6-4√2)=(6-4√2+6+4√2)/(36-32)=12/4=3