y＝3x+4/(x-1)+1→3x²-(y+2)x+y+3＝0.△＝(y+2)²-12(y+3)≥0→y²-8y-32≥0→y≥4+4√3,y≤4-4√3.而x>1,故所求最小值为：y|min＝4+4√3.此时易得，x＝(3+2√3)/3.
