√(X^2-2X+1)=√(X-1)^2=|X-1|,√(X^2-6X+9)=|X-3|,不等式就是:|X-1|+|X-3|≥4,①当X<1时,不等式化为:-(X-1)-(X-3)≥4,-2X≥0,X≤0,得:X≤0,②当1≤X≤3时,不等式化为:(X-1)-(X-3)≥4,2≥4,无解,③当X>3时,不等式化为(X-1)+(X-3)≥4,2X≥8,X≥4,得:X≥4,综上所述,原不等式的解集为:X≤0或X≥4。