y=3√(x-1)+√(12-2x)
定义域： 1≤x≤6
令x=3.5+2.5cosα, 0 ≤α≤π,0 ≤α/2≤π/2
y=√[12-(7+5cosα)]+3√(3.5+2.5cosα-1)
=√[5(1-cosα)]+3√[2.5(1+cosα)]
=√(10sin²α/2)+√(5cos²α/2)
=√10sin(α/2)+3√5cos(α/2)
=5sin(α/2+β)≤5
最大值为5错了😣是3√5唉，考试考完了😱