a,2x +3/10=1/5/6.6/11 b,2/1/4:(x-7/1/3)=-1,5 c,2x²-72=0

`a) 2x+ 3/10 = (1/5/6) . 6/11`

`⇒ 2x + 3/10 = 6/5 . 6/11`

`⇒ 2x + 3/10 = 36/55`

`⇒ 2x             = 36/55 -3/10`

`⇒ 2x             = 39/110`

`⇒   x = 39/110 :2`

`⇒   x = 39/220`.

`Vậy`, `x=39/220`.

`b) 2/1/4 : (x- (7/1/3) ) = -1,5`

`⇒ 8 : (x-21) =-1,5`

`⇒ x-21 = 8: (-1,5)`

`⇒ x-21 = (-16)/3`

`⇒ x      = (-16)/3 +21`

`⇒ x      = 47/3`

`Vậy`, `x= 47/3`.

`c) 2x^2 -72-0`

`⇒ 2x^2 =72`

`⇒   x^2 = 72/2`

`⇒   x^2 = 36`

`TH1: x^2 = 6^2`

`⇒ x=6`

`TH2: x^2 = (-6)^2`

`⇒ x = (-6)`

`Vậy`, `x∈{6;-6}`.

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