Question

Tìm n thuộc N:

1+2+3+4+5+......+n=528

Answer 1

\(1+2+3+4+5+...+n=528\)

\(\Rightarrow\left(n+1\right).n\div2=528\)

\(\Rightarrow\left(n+1\right).n=528\times2\)

\(\Rightarrow\left(n+1\right).n=1056\)

\(\Rightarrow\left(n+1\right).n=33.32\)

\(\Rightarrow n=32\)

Answer 2

1+2+3+4+5+...+n=528

528=(1+n).n : 2

528.2=(n+1).n

1056=(n+1).n

32.33=(n+1).n

=> n=32