f(x)=x²-3x+lnx
f'(x)=2x-3+1/x=(2x²-3x+1)/x=(2x-1)(x-1)/x
得极值点x=1/2, 1
f(1/2)=1/4-3/2-ln2=-5/4-ln2为极大值;
f(1)=1-3+0=-2为极小值