Question

Sa se afle x din x+(1+2+3+4+.......+49)=1625

Answer 1

se aplica formula n×(n+1):2


49 ×(49+1):2

=49×50:2
=2450 :2
=1225

×+1225=1625
×=1625-1225
×=400

Answer 2

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

x+49×50:2=1625

x+49×25=1625

x=1625-49×25

x=1625-1225

x=400

R: x=400