Ta có:2+4+6+...+20=(20+2)+(18+4)+(16+6)+(14+8)+(12+10)=22+22+22+22+22=22.5=110
\(2+4+6+...+20\)
\(=\left(20+2\right)\left(\frac{20-2}{2}+1\right):2\)
\(=22\times10:2=110\)
#Hoktoots
Giải :
2 + 4 + 6 +... + 20
= ( 2 + 20 ) + ( 4 + 18 ) + ( 6 + 16 ) + ( 8 + 14 ) + ( 10 + 12 )
= 22 . 5
= 110
Hok tốt ạ :33
Day tren co so cac so hang la:
(20-2):2+1=10(so)
Tong cua day tren la:
(2+20).10:2=110
Dung thi k ung ho minh nha!!!Thanks!!!
