If the area of the region {(x,y):x2−2≤y≤x} is A, then 6A+162 is equal to ______.
Answer: 27
Solution
On [1,2] the lower curve is y=2−x2 and on [2,2] it is y=x2−2, with y=x as the upper boundary; the line meets 2−x2 at x=1 and x2−2 at x=2. Hence A=∫12(x−(2−x2))dx+∫22(x−(x2−2))dx=29−382. Therefore 6A=27−162, and 6A+162=27.