b.3x + 5 - 712 . (x -1) = 1110 c.3x - 7 .(x+3) = 8x + 215

Đáp án:

Giải thích các bước giải:

`b) 3x + 5 - 712 . (x - 1) = 1110`

`⇒ 3x + 5 - (712x - 712) = 1110`

`⇒ 3x + 5 - 712x + 712 = 1110`

`⇒ 717 - 709x = 1110`

`⇒ 709x = -393`

`⇒ x = -393/709`

Vậy `x = -393/709`

`c) 3x - 7 . (x + 3) = 8x + 215`

`⇒ 3x - (7x + 21) = 8x + 215`

`⇒ 3x - 7x - 21 = 8x + 215`

`⇒ -4x - 8x = 215 + 21`

`⇒ -12x = 236`

`⇒ x = -59/3`

Vậy `x = -59/3`

$\text{b) 3x + 5 - 712(x - 1) = 1110}$

$\text{3x + 5 - (712x - 712) = 1110}$

$\text{3x + 5 - 712x + 712 = 1110}$

$\text{717 - 709x = 1110}$

$\text{709x = 717 - 1110}$

$\text{709x = -393}$

$\text{x = -393 : 709}$

$\text{x = -$\dfrac{393}{709}$}$

$\text{c) 3x - 7(x + 3) = 8x + 215}$

$\text{3x - (7x + 21) = 8x + 215}$

$\text{3x - 7x - 21 = 8x + 215}$

$\text{-4x - 21 = 8x + 215}$

$\text{-4x - 8x = 215 + 21}$

$\text{-12x = 236}$

$\text{x = 236 : (-12)}$

$\text{x = -$\dfrac{59}{3}$}$

$\textit{Ha1zzz}$