If the area of the region {(x,y):4−x2≤y≤x2,y≤4,x≥0} is (α802−β),α,β∈N, then α+β is equal to ______.
Answer: 22
Solution
For x≥0 the region is ∣4−x2∣≤y≤x2 together with y≤4. The lower curve y=∣4−x2∣ is 4−x2 for 0≤x≤2 and x2−4 for x>2. The requirement ∣4−x2∣≤x2 forces x≥2. For 2≤x≤2 the strip runs from y=4−x2 to y=x2; for 2≤x≤22 it runs from y=x2−4 to the cap y=4, beyond which the lower bound exceeds 4. Hence