1.f(1/2)=f(2-1/2)=f(3/2) f(1/3)=f(2-1/3)=f(5/3)
当x≥1时,f(x)=lnx 为增函数
2>5/3>3/2 则f(2)>f(1/3)>f(1/2) 选c
2.a=2,b=1,c=√3
设P点坐标为(x,y) x∈[-2,2] M(x,0)
F1(-√3,0) F2(√3,0)
PF1=(-√3-x,-y) PF2=(√3-x,-y)
PF1*PF2=x^2-3+y^2 (1)
x²/4+y²=1 将y²=1-x²/4代入(1):PF1*PF2=3x²/4-2
当PF1*PF2=3x²/4-2