a) (102+112+122) : (132+142)
b) 1x2x3....x9-1x2x3...x8-1x2x3....x7x82
1x2x3...9-1x2x3...8-1x2x3...82
Đáp số và cách làm
1x2+1x2x3+1x2x3x4+1x2x3x4x5+....+1x2x3...99x100
2/1x2x3 + 2/2x3x4 + 2/3x4x5 + ... + 2/36x37x38 + 2/37x38x39
1x2x3+2x3x4+3x4x5+...+98x99x100
1x2x3+4x5x6+...+100x101x 102
1x2x3+2x3x4+3x4x5+....+2018x2019
1/1x2x3 + 1/2x3x4 + ... + 1/98x99x100
A=1x2x3+2x3x4+.......+20x21x22 cần giúp
