`d) ( 4x - 5 )( 5/4x - 2 ) = 1 1/3`

Đáp án:

`(4x - 5).(5/4x - 2)= 1 1/3`

`<=> 5x^2 - 8x - 25/4x + 10= 4/3`

`<=> 5x^2 - 57/4x + 10 = 4/3`

`<=> 5x^2 - 57/4x + 26/3 = 0`

`<=> 60x^2 - 171x + 104 = 0`

`<=> x^2 - 171/60x + 26/15 = 0`

`<=> x^2 - 2.x . 171/120 + (171/120)^2 - 1427/4800= 0`

`<=> (x - 171/120)^2 = 1427/4800`

`<=>` \(\left[ \begin{array}{l}x=\dfrac{171 + \sqrt{4281}}{120}\\x=\dfrac{171 - \sqrt{4281}}{120}\end{array} \right.\) 

Vậy `x in {(171 +- \sqrt{4281})/120}`

$@dariana$