Câu hỏi của Lê Văn Cảnh

Question

Cho 12+22+32+...+102=385.Tinh 22+42+62+...+202

Nguyễn Thanh Thủy · Accepted Answer

đặt A= 22+42+62+82+.......+202

$\Leftrightarrow A$= 12.22+22.22+22.32+...+22.102

$\Leftrightarrow$A= 22(12+22+32+...+102)

$\Leftrightarrow$A=4.385=1540Câu trả lời: đặt A= 22+42+62+82+.......+202

$\Leftrightarrow A$= 12.22+22.22+22.32+...+22.102

$\Leftrightarrow$A= 22(12+22+32+...+102)

$\Leftrightarrow$A=4.385=1540

Lê Việt Anh · Answer

Đặt T = $1^2+2^2+....+10^2=385$

$\Rightarrow T\times2^2=1^2.2^2+2^2.2^2....+10^2.2^2=385.2^2$

$\Rightarrow T\times2^2=\left(1.2\right)^2+\left(2.2\right)^2....+\left(10.2\right)^2=385.2^2$

$\Rightarrow T\times2^2=\left(2\right)^2+\left(4\right)^2+....\left(20\right)^2=385.2^2$

$\Rightarrow T\times2^2=S=385.2^2$

$\Rightarrow S=385\times4$Câu trả lời: Đặt T = $1^2+2^2+....+10^2=385$

$\Rightarrow T\times2^2=1^2.2^2+2^2.2^2....+10^2.2^2=385.2^2$

$\Rightarrow T\times2^2=\left(1.2\right)^2+\left(2.2\right)^2....+\left(10.2\right)^2=385.2^2$

$\Rightarrow T\times2^2=\left(2\right)^2+\left(4\right)^2+....\left(20\right)^2=385.2^2$

$\Rightarrow T\times2^2=S=385.2^2$

$\Rightarrow S=385\times4$

Đại số lớp 8