The area (in sq. units) of the region A={(x,y):(x−1)[x]≤y≤2x,0≤x≤2}, where [t] denotes the greatest integer function, is:
(A)382−1
(B)342−21
(C)382−21✓ Correct
(D)342+1
Answer: (C)
Solution
Break the region at x=1. For 0≤x<1 the greatest integer [x]=0, so the lower boundary is y=0; for 1≤x<2, [x]=1, so the lower boundary is y=x−1. The area is ∫022xdx less the triangle of base 1 and height 1 sitting under y=x−1: [34x3/2]02−21=382−21.
JEE Main · 2020 · 05 Sep 2020 · Shift 2 · Single correct option