मराठी

If f : R → R is defined by f(x)=2x-74, show that f(x) is one-one and onto.

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प्रश्न

If f : R `rightarrow` R is defined by `f(x) = (2x - 7)/4`, show that f(x) is one-one and onto.

बेरीज
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उत्तर

Given, `f(x) = (2x - 7)/4`

For one-one

Let x, x2 ∈ R

f(x1) = f(x2)

`(2x_1 - 7)/4 = (2x_2 - 7)/4`

`\implies` 2x1 – 7 = 2x2 – 7

`\implies` 2x1 = 2x2

`\implies` x1 = x2

So, f(x) is a one-to-one function.

For onto

Put `y = (2x - 7)/4`

`\implies` 4y = 2x – 7

`\implies` 4y + 7 = 2x

`\implies` `x = (4y + 7)/2`    ∀ y ∈ R ∃ a unique x ∈ R

Therefore, f(x) is onto.

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