~ gửi bạn ~
Đặt `x = 1/{5741}; y = 1/{3759},` ta có:
`A = (4 + 7x)*y - 4y*(1 + 2x) + y + xy`
` = 4y + 7xy - 4y - 8xy + y + xy`
` = y`
`=> A = 1/{3759}`
___________________________________
Đặt `x = 1/{3150}; y = 1/{6547},` ta có:
`B = (2 + x)*3y - 3x*(4 - y) + 12x - 6xy`
` = 6y + 3xt - 12x + 3xy + 12x - 6xy`
` = 6y`
`=> B = 6/{6547}`