Question

afla valoarea lui x din expresia:x+(1+2+3+4+.....+49)=1625

Answer 1

$x + (1 + 2 + 3 + 4 + ... + 49) = 1625 \\ \\ x + (49 \times 50 \div 2) = 1625 \\ \\ x + (49 \times 25) = 1625 \\ \\ x + 1225 = 1625 \\ \\ x = 1625 - 1225 \\ \\ x = 400$

Answer 2

x+ 49 x 50 / 2 = 1625
1+2+3+...+49=49 x 50 / 2   → n(n+1)/2 formula pentru a afla cat face adunarea
x + 49 x 25 =1625
x+1225=1625
x=1625-1225
x=400