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Tamil Nadu Board of Secondary EducationHSC Science Class 11

Find the constant b that makes g continuous on (-∞,∞). bifbifg(x)={x2-b2if x<4bx+20 if x≥4 - Mathematics

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Question

Find the constant b that makes g continuous on `(- oo, oo)`.

`g(x) = {{:(x^2 - "b"^2,"if"  x < 4),("b"x + 20,  "if"  x ≥ 4):}`

Sum
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Solution

`g(x) = {{:(x^2 - "b"^2,"if"  x < 4),("b"x + 20,  "if"  x ≥ 4):}`

Given g is continuous on R.

∴ g(x) is continuous at x = 4.

`lim_(x -> 4^-) g(x) =  lim_(x -> 4^+) g(x)`

`lim_(x ->4^-) (x^2 - "b"^2) =  lim_(x -> 4^+) ("b"x + 20)`

42 – b2 = b × 4 + 20

16 – b2 = 4b + 20

b2 + 4b + 20 – 16 = 0

b2 + 4b + 4 = 0

(b + 2)2 = 0

b + 2 = 0 ⇒ b = – 2

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Chapter 9: Differential Calculus - Limits and Continuity - Exercise 9.5 [Page 128]

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Samacheer Kalvi Mathematics - Volume 1 and 2 [English] Class 11 TN Board
Chapter 9 Differential Calculus - Limits and Continuity
Exercise 9.5 | Q 12 | Page 128

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