(2√2)^2 = 2^a *2^b
2^3 = 2^(a+b)
a+b=3
a^2 + b^2 + 2ab=9
ab=1/2 [9-(a^2 +b^2)]
=1/2 {9-[a^2 +(3-a)^2}
=-(a^2 -3a)
=-(a-3/2)^2 + 9/4
ab的最大值=9/4
(2√2)^2 = 2^a *2^b
2^3 = 2^(a+b)
a+b=3
a^2 + b^2 + 2ab=9
ab=1/2 [9-(a^2 +b^2)]
=1/2 {9-[a^2 +(3-a)^2}
=-(a^2 -3a)
=-(a-3/2)^2 + 9/4
ab的最大值=9/4