Question

Dacă 1+2+3+... +11=a și 9+10+11... +18=b atunci calculati a+b​

Answer 1

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

11*(11+1):2

11*12:2

11*6=66

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

(1+2+3+....+18)-(1+2+3+...+8)

18*(18+1):2-8*(8+1):2

18*19:2-8*9:2

9*19-4*9

171-36=135

a+b=66+135=201

Answer 2

Răspuns:

a=1+2+...+11=(11·12) :2=11·6=66

b=9+10+...+18=(1+2+3+....+18)-(1+2+3+...+8)=18·19:2-8·9:2=9·19-4·9=171-36=135

a+b=66+135=201