4a^2+b^2=6 转化椭圆方程
a^2/(√6/2)^2+b^2/(√6)^2=1
X=√6/2*cosA/,y=√6sinA
X+Y=√6/2*cosA+√6sinA
=√6(1/2*cosA/+sinA)
令tanB=1/2,cosB=2/√5
X+Y=√6/cosB*(sinB*cosA+sinA*cosB)
=√30/2*sin(A+B)
(X+Y)max=√30/2
(X+Y)min=0