$\text{Bài 2:}$
`1, 4.(x-1/4) - 3(x+2/3) = 0`
`⇔ 4.(x-1/4) = 3(x+2/3)`
`⇔ 4x - 1 = 3x + 2`
`⇔ 4x - 3x = 2 + 1`
`⇔ x = 3`
`2, 1/(2.3) + 1/(3.4) + 1/(4.5) +...+ 1/(99.100)`
`= 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + ...+ 1/99 - 1/100`
`= 1/2 - 1/100`
`= 50/100 - 1/100 = 49/100`