Question

Calculati urmatoarele sume:
a)2+3+4+...50;
b) 1+2+3+...124;
e) 2+4+6+...+600;
f) 15+16+17+...+70.
Vã rog dau coroanã!!!

Answer 1

Răspuns:

Explicație pas cu pas:

a)2+3+4+...50= (50·51/2)-1= (25·21)-1= 525-1= 524

b) 1+2+3+...124= 124·125/2= 62·125= 7750

e) 2+4+6+...+600= 2(1+2+3+...+300)= 2·300·301/2= 90300

f) 15+16+17+...+70= 1+2+3+...+70 -(1+2+3+...14) = 70·71/2- 14·15/2=

35·71-7·15=2485-105=2380