If the area of the region {(x,y):0≤y≤min{2x,6x−x2}} is A , then 12 A is equal to ______
Answer: 304
Solution
The curves y=2x and y=6x−x2 meet where 2x=6x−x2⇒x2−4x=0⇒x=0,4.
For 0≤x≤4, checking at x=2: 2x=4, 6x−x2=8, so 2x≤6x−x2 and min{2x,6x−x2}=2x.
The parabola y=6x−x2 meets the x-axis at x=0 and x=6. For 4≤x≤6, checking at x=5: 2x=10, 6x−x2=5, so 6x−x2≤2x and min{2x,6x−x2}=6x−x2; beyond x=6, 6x−x2<0, outside the region y≥0.