3x²-6x+8=3x²-6x+3+5=3(x²-2x+1)+5=3(x-1)²+53(x-1)²>=03(x-1)²+5>=5所以y=√(3x²-6x+8)>=√5所以y最小值=√5
f(x)=2(1-cos2x)/2+2√3sinxcosx=1-cos2x+√3sin2x=2sin(2x-z)+1其中tanz=1/√3z=π/6f(x)=2sin(2x-π/6)+10-π/6<2x-π/6<7π/6所以-1/2所以0-2-2+m0所以-2+m>=0且2+m<3m>=2,m<1不成立