Question

[Nguyen sy tuan]

Tim so tu nhien n biet:

1+2+3+4+.....+ n=465 

Giao the nao day !

Answer 1

[Sakuraba Laura]

\(1+2+3+4+...+n=465\)

\(\Rightarrow\left(n+1\right).n\div2=465\)

\(\Rightarrow\left(n+1\right).n=465.2\)

\(\Rightarrow\left(n+1\right).n=930\)

\(\Rightarrow\left(n+1\right).n=31.30\)

\(\Rightarrow n=30\)

Vậy \(n=30\)

Answer 2

[Sooya]

1+2+3+4+..+n=465

=> 465 = (1+n).n : 2

=> 465.2=(1+n).n

=> 930=(1+n).n

có 930 = 2.3.5.31

=> 930 = (2.3.5).31

=> 930 = 30.31

=> n=30

vậy n = 30