Question

URGENT PENTEU MAINE!​

Answer 1

rezolvare in atasament

Answer 2

Răspuns:

Explicație pas cu pas:

a+b=151

a-b=51 Adunam cele 2 relatii.  ⇒2a+b-b=102 ⇒2a=202 ⇒a=101  

⇒b=a-51=101-51=50  b=50  

Verificare: a+b=101+50=151

La acest exercitiu se aplica formula sumei lui Gauss: 1+2+3+...+n=n(n+1)/2

a) 1+2+3+...40=40·(40+1)/2=20·41=820

b) 3+6+9+...+120=3·(1+2+3+...40)=3·40·(40+1)/2=3·20·41=3·820=2460