1 + 2 + 3 + ... + x = 210
=> x.(x + 1) : 2 = 210
=> x.(x + 1) = 420
=> x.(x + 1) = 20.21
=> x = 20
Các câu hỏi tương tự
A] X-1,25x4= 2,5 b] [ X CONG 1 ] CONG [ X CONG 2] CONG [ X CONG 3 CONG ] .............. CONG [ X CONG 20] = 750 C ] [ X CONG 1] CONG [X CONG 2 ] CONG [ X CONG 3 ] CONG ........... CONG [ X CONG 10] = 175
1 CONG 3 CONG 5 CONG .........CONG [ 2 x X CONG 1] = 169
[ X 1 cong ] cong [ X 2 cong ] cong[ X3 cong] CONG .............. CONG 20 = 750
1 CONG 3 CONG 5 CONG CONG .......... CONG [ 2x X CONG 1] =169
1 CONG 3 CONG 5 CONG ............... CONG [ 2x X 1] CONG 169
tim so tu nhien x
3 mu x cong 3 mu x cong 1 cong 3 mu x cong 2 = 1053
x cong 1 cong x cong 2 cong ...x cong 100 bang 5050
1) (-1005).(x cong 2 ) bang 0
2) x cong x cong x cong 91 bang -2
3) / 5x cong 1/ bang 11
( thong cam nha , may mik k viet dc dau cong vs bang )
mik dg gap , giup mik nhe !
[ 2 CONG X ] CONG [ 4 CONG X ] CONG [ 6 CONG X ] CONG .......................... CONG [ 52 CONG X ] = 780