f(x)=-2a(cosx)^2 -2√2asinx+3a+b
=2a(sinx)^2-2√2asinx+3a+b-2
=2a[sinx-√2/2)^2+2a+b-2
x=π/4 f(x)最小=2a+b-2=-5
x=3π/4,f(x)最大=4a+b-2=1
2a=6,a=3,b=-9
f(x)=-2a(cosx)^2 -2√2asinx+3a+b
=2a(sinx)^2-2√2asinx+3a+b-2
=2a[sinx-√2/2)^2+2a+b-2
x=π/4 f(x)最小=2a+b-2=-5
x=3π/4,f(x)最大=4a+b-2=1
2a=6,a=3,b=-9