Question

2+4+6+....+2n = 10100 

n=?

Answer 1

\(2+4+6+...+2n=\frac{\left(2+2n\right).n}{2}=n\left(n+1\right)=10100=100.101\Rightarrow n=100\)

Answer 2

ta có: 2+4+6+8+.....+2n=10100

2(1+2+3+4+...+n)=10100

1+2+3+4+....+n=5050

=> (n+1).n:2=5050

     (n+1).n=10100

=> (n+1)=51     Vậy n=50

Answer 3

= 100