a) 1/3 + 1/7 = 7/21 + 3/21 = 10 /21
→ le aduc la acelasi numitor comun 21
→ amplific prima fractie cu 7, iar pe a doua cu 3
→ adun numaratorii si scriu numitorul
b) 2 / 3 + 3 / 7 + 4 / 21= (7 x 2) / ( 7 x 3) + ( 3 x 3) / ( 3 x 7) + 4/21 =
= 14/21 + 9/21 + 4/21 =
= ( 14 + 9 + 4) / 21 =
= 27/21 =
= 1 intreg si 6/21
c) 4 / 5+1+ 2 / 6 = ( 6 x 4) / 30 + 30 / 30 + (5 x 2) / ( 5 x 6) =
= 24 /30 + 30/30 + 10/30 =
= 64/30 =
= 32/15 =
= 2 intregi si 2/15
4 / 5+1+ 2 / 6 = 4/5 + 1 + 1/3 = 12/15 + 15/15 + 5/15 = 32/15 = 2 intregi 2/15
→ am simplificat fractia 2/6 prin 2 = 1/3
→ aduc fractiile la acelasi numitor 15,amplific pe 4/5 cu 3, pe 1/3 cu 5
1=> intreg = 15/15
