Question

n=?

1+2+3+...+n=55

Dau coronița !

Answer 1

1+2+3+...+n=55
$\frac{n \times (n + 1)}{2} = 55$
n x (n+1)=110=>
=>n=10

Answer 2

1+2+3+...+n=55
dar 1+2+3+...+n=n(n+1)/2     ⇒
⇒n(n+1)/2=55
⇒n(n+1)=110
⇒n=10



Sper ca te-am ajutat ! :)