Let [t] denote the greatest integer less than or equal to t. If the function f(x) = cases b2 ( 2 [ 2( x + x) x ] ), & x < 0 \ x - 12 2xx3, & x > 0 \ a, & x = 0 cases is continuous at x = 0, then a2 + b2 is equal to :
- 12
- 58
- 34
- 916
Answer
(3) 34
Solution
Right-hand limit:
x 0+ x - x xx3
= x 0+ xx 1 - xx2 = 1 12 = 12 ⇒ RHL = 12
Left-hand limit: ( x + x) x = 2 x + x x = 1 - 2 x + 12 2x
For small x < 0, 2x < 0, so this value is slightly less than 1.
⇒ 2( x + x) x is slightly less than 2 1.57 (and greater than 1)
⇒ [ 2( x + x) x ] = 1
⇒ LHL = b2 2 = b2
Continuity at x = 0: b2 = a = 12
∴ a2 + b2 = 14 + 12 = 34
Answer: (3)