Question

Va rog ajutatima am nevoie urgent! Daca 1+2+3+......+11=a si 9+10+11+....+18=b, atunci calculati a+b. DAU LA FIECARE RASPUNS CORECT

Answer 1

1+2+3+......+11=a

a= 11 x 12 / 2 = 11 x 6 =66

a=66

9+10+11+....+18=b

1+8+2+8+3+8+...10+8=b

(1+2+3+...+10) + 8 x 10=b

10 x11/2 + 80 =b

55 + 80 = b

135 = b

a + b = 66 + 135 = 201

Answer 2

6a = 1 + 2 + 3 + ...... + 11

a = 11 × ( 1 + 11 ) / 2

a = 11 × 12 / 2

a = 11 × 6

a = 66

_______________________

b = 9 + 10 + 11 + ..... + 18

→ stabilesc cati termeni are suma cu ratia = 1

18 - 9 + 1 = 10 termeni are suma

→ aplic formula sumei lui Gauss

b = 10 × ( 9 + 18 ) / 2

b = 5 × 27

b = 135

_______________

a + b = 66 + 135 = 201 → suma numerelor