如图,在平面直角坐标系\(xOy\)中,点\(A(0,3)\),直线\(l \):\(y=2x-4.\)设圆\(C\)的半径为\(1\),圆心在\(l \)上\(.\)
\((1)\)若圆心\(C\)也在直线\(y=x-1\)上,过点\(A\)作圆\(C\)的切线,求切线的方程;
\((2)\)若圆\(C\)上存在点\(M\),使\(MA=2MO\),求圆心\(C\)的横坐标\(a\)的取值范围.
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