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Check if the following function has an inverse function. If yes, find the inverse function. f(x) = {x+7x<08-xx≥0

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Question

Check if the following function has an inverse function. If yes, find the inverse function.

f(x) = `{(x + 7, x < 0),(8 - x, x ≥ 0):}`

Sum
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Solution 1

f(x) = `{(x + 7, x < 0),(8 - x, x ≥ 0):}`

If x < 0, x + 7 < 7

If x ≥ 0, – x ≤ 0 so that 8 – x ≤ 8

∴ Range = `(- ∞, 8)`

∴ for y = 10, we cannot find x such that f(x) = y

∴ f is not onto

∴ f–1 does not exist.

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Solution 2

f(x) = `{(x + 7, x < 0),(8 - x, x ≥ 0):}`

∴ f(– 1) = – 1 + 7 = 6

∴ f(2) = 8 – 2 = 6

∴ f(– 1) = f(2) but – 1 ≠ 2

∴ f is not one-one

∴ f–1 does not exist.

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Chapter 6: Functions - Exercise 6.2 [Page 128]

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