Question

Biết 1^2 +2^2 +3^2+....+ 50^2=42925

Tính tổng S= 2^2+ 4^2 +6^2 +.... +100^2

Mn giúp mình đc ko ạ( cần gấp ạ)

Answer 1

\(1^2+2^2+3^2+...+50^2=42925\)

\(\Rightarrow2^2\left(1^2+2^2+3^2+....+50^2\right)=42925.2^2=171700\)

\(\Rightarrow2^2+4^2+6^2+...+100^2=171700\)

Answer 2

\(S=2^2+4^2+6^2+...+100^2\\ =1^2.2^2+2^2.3^2+...+2^2.50^2\\ =2^2\left(1^2+2^2+3^2+...+50^2\right)\\ =4.42925=171700\)