Question

Afla valoarea lui X din expresia X+(1+2+3+4+...+49)=1625

Answer 1

x + (1 + 2 + .. + 49) = 1625

x + 49×50:2 = 1625

x = 1625 - 49×25

x = 1625 - 1225

x = 400

Answer 2

Răspuns:

x+(1+2+3+...+49)=1625

suma lui Gauss

(1+2+3+...+49)=(49·50):2=1225

x+1225=1625

x=1625-1225

x=400