`a):`
`2x - 7 = 0`
`⇔ 2x = 7`
`x = 7/2`
Vậy `x = 7/2`
`b):`
`1/3x - 2/5 = (2x)/7 + 3`
`⇔ 35x − 42 = 15 × 2x + 315`
`⇔ 35x − 42 = 30x + 315`
`⇔ 35x − 42 − 30x = 315`
`⇔ 5x − 42 = 315`
`⇔ 5x = 315 + 42`
`⇔ 5x = 357`
`x = 357/5`
Vậy `x = 357/5`
`c):`
`- 3x^2 + 5x = 0`
`⇔ x(− 3x + 5) = 0`
`x = 0`
`x = 5/3`
Vậy `x = 0`
`x = 5/3`
Cho mình xin hay nhất nha bạn!!!!!
@Drew Mclntyre