( x -5 /2 ) 2 = 9/ 4

`(x-5/2)^2=9/4`

`<=>(x-5/2)^2-9/4=0`

`<=>(x-5/2)^2-(3/2)^2=0`

`<=>(x-5/2-3/2)(x-5/2+3/2)=0`

`<=>(x-4)(x-1)=0`

`<=>[(x-4=0),(x-1=0):}`

`<=>[(x=4),(x=1):}`

`Vậy` `x\in{4;1}`