`(4x-1)^2 = 25*9`
`<=> (4x-1)^2 = 225`
`<=> [(4x-1=15),(4x-1=-15):}`
`<=> [(4x=15+1=16),(4x=-15+1=-14):}`
`<=> [(x=16/4 = 4),(x = -14/4 =-7/2):}`
Vậy `S={4;-7/2}`
\(\left(4x-1\right)^2=225\\ =>\left(4x-1\right)^2=15^2\\ =>4x-1=15\\ =>4x=16\\ =>x=4\)