Jehehrhrhrhrhhrhrhr help me pls

Đáp án`+`Giải thích các bước giải:

Bài ` 2: `

` a) x/-5 = 4/21 `

` x xx 21 = (-5) xx 4 `

` x xx 21 = -20 `

` x = (-20) : 21 `

` x = -20/21 `

Vậy: ` x = -20/21 `

` b) (2x - 1/4)^2 = 49/25 `

` (2x - 1/4)^2 = (±7/5)^2 `

TH ` 1: `

` 2x - 1/4 = 7/5 `

` 2x = 7/5 + 1/4 `

` 2x = 33/20 `

` x = 33/20 : 2 `

` x = 33/40 `

TH ` 2: `

` 2x - 1/4 = -7/5 `

` 2x = (-7/5) + 1/4 `

` 2x = -23/20 `

` x = (-23/20) : 2 `

` x = -23/40 `

Vậy: ` x in {33/40; -23/40} `

`color{pink}{#Ruki}`