`a, x >= 4 -> x - 4 = -x + 4`
`-> x = 4`.
`x <= 4-> 4 - x= -x + 4`
`-> x <=4`.
`-> x <= 4`.
`b, (x-1)^2 = 5(x+1)^2`
`-> x^2 - 2x + 1 = 5x^2 + 10x + 5`
`-> 4x^2 + 12x - 4 = 0`
`-> x^2 + 3x + 1=0`
`\Delta = 9 - 4 =5`
`-> {(x_1 = (-3 + sqrt 5)/2), (x_2 = (-3 - sqrt 5)/2):}`
a: =>x-4<=0
=>x<=4
b: \(\Leftrightarrow5x^2+10x+5-x^2+2x-1=0\)
\(\Leftrightarrow4x^2+12x+4=0\)
hay \(x\in\left\{\dfrac{-3+\sqrt{5}}{2};\dfrac{-3-\sqrt{5}}{2}\right\}\)
\(a,\left[{}\begin{matrix}x-4=x-4\left(lđ\right)\\x-4=-x+4\end{matrix}\right.=>x+x-4-4=0\\ 2x-8=0\\ 2x=8\\ x=4\\ b,x^2-2x+1-5x^2-10x-5=0\\ -4x^2-12x-4=0\\ -4\left(x^2+3x+1\right)=0\\ x^2+3x+1=0\\ =>x=-\dfrac{3+\sqrt{5}}{2};x=-\dfrac{3-\sqrt{5}}{2}\)
