Question

Tính nhanh :

\(\left(50^2+48^2+46^2+...+4^2+2^2\right)-\left(49^2+47^2+...+3^2+1^2\right)\)

Answer 1

há há.. bài này mà lớp 8 hã?

\(50^2+48^2+...+4^2+2^2-49^2-47^2-...-1^2\)

\(=50^2-49^2+48^2-47^2+...+2^2-1^2\)

\(=\left(50+49\right)\left(50-49\right)+\left(48+47\right)\left(48-47\right)+...\left(2+1\right)\left(2-1\right)\)

\(=99+95+...+3\)

\(=\frac{\left(99+3\right)\left(99-3\right):4+1}{2}\)

\(=1275\)

Answer 2

ta bo ngoac roi tinh

kllllet qua cuoi cung a1275