BITSAT2019MathematicsArea Under CurvesActual
The point ( [ P + 1 ] , [ P ] ) (where, [ x ] is the greatest integer function) lying inside the region bounded by the circle x 2 + y 2 - 2 x - 15 = 0 and x 2 + y 2 - 2 x - 7 = 0 , then
Options
- AP ∈ [ - 1 , 2 ) - 0 , 1
- BP ∈ [ - 1 , 0 ) ∪ ( 0 , 1 ) ∪ ( 1 , 2 ]
- CP ∈ ( - 1 , 2 )
- DNone of these
Correct answer
D. None of these
Step-by-step solution
[ P + 1 ] = [ P ] + 1 , Let [ P ] = n , then n is integer ∴   ( [ P + 1 ] , [ P ] ) = ( n + 1 , n ) lie inside the region of circles S 1 = x 2 + y 2 - 2 x - 15 = 0 , C 1 = ( 1 , 0 ) , r 1 = 4 and S 2 = x 2 + y 2 - 2 x - 7 = 0 , C 2 = ( 1 , 0 ) , r 2 = 2 2 Both circles are concentric. ∴   ( n + 1 ) 2 + n 2 - 2 ( n + 1 ) - 7 > 0 and ( n + 1 ) 2 + n 2 - 2 ( n + 1 ) - 15 < 0 ⇒ 4 < n 2 < 8 Which is not possible for any integer.