a) điều kiện xát định là \(x>1\)
b) \(A=\sqrt{x-\sqrt{x^2-4x+4}}=\sqrt{x-\sqrt{\left(x-2\right)^2}}\)
th1: \(x\ge2\) thì : \(A=\sqrt{x-\sqrt{\left(x-2\right)^2}}=\sqrt{x-x+2}=\sqrt{2}\)
th2: \(x< 2\) thì \(A=\sqrt{x-\sqrt{\left(x-2\right)^2}}=\sqrt{x-2+x}=\sqrt{2x-2}\)
vậy .........................................................................................