-4/10^(1/2)≤2a+b≤4/10^(1/2)
设t=2a+b,则有4a^2+(t-2a)^2+a(t-2a)=1,化简为:6*(a-t/4)^2=1-10t^2/16,等式恒成立,则有1-10t^2/16≥0,解得-4/10^(1/2)≤t≤4/10^(1/2),4/10^(1/2)读作根号10分之4,
即-4/10^(1/2)≤2a+b≤4/10^(1/2).
-4/10^(1/2)≤2a+b≤4/10^(1/2)
设t=2a+b,则有4a^2+(t-2a)^2+a(t-2a)=1,化简为:6*(a-t/4)^2=1-10t^2/16,等式恒成立,则有1-10t^2/16≥0,解得-4/10^(1/2)≤t≤4/10^(1/2),4/10^(1/2)读作根号10分之4,
即-4/10^(1/2)≤2a+b≤4/10^(1/2).