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Find the relationship between a and b so that the function f defined by f(x) = {๐‘Žโข๐‘ฅ + 1, if ๐‘ฅ โ‰ค 3, ๐‘โข๐‘ฅ + 3, if ๐‘ฅ > 3 is continuous at x = 3.

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Question

Find the relationship between a and b so that the function f defined by f(x) = `{(ax + 1", if"  x<= 3),(bx + 3", if"  x > 3):}` is continuous at x = 3.

Sum
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Solution

f(x) = `{(ax + 1", if"  x<= 3),(bx + 3", if"  x > 3):}`

At x = 3

f(x) = ax + 1

When x = 3

L.H.L = `lim_(x -> 0)` + f(x)

= `lim_(x -> 0)` + (ax + 1)

= 3a + 1

f(3) = 3a + 1

f(x) = bx + 1 when x > 3

R.H.L = `lim_(x -> 0)` + f(x)

= `lim_(x -> 0)` + (bx + 3)

= 3b + 3

3a + 1 = 3b + 3

a = b + `2/3`

The value of a can be found for any arbitrary value of b.

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Chapter 5: Continuity and Differentiability - Exercise 5.1 [Page 160]

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NCERT Mathematics Part 1 and 2 [English] Class 12
Chapter 5 Continuity and Differentiability
Exercise 5.1 | Q 17 | Page 160

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