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Check the injectivity and surjectivity of the following function. f : R → R given by f(x) = x3 - Mathematics and Statistics

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प्रश्न

Check the injectivity and surjectivity of the following function.

f : R → R given by f(x) = x3 

बेरीज

उत्तर

f : R → R given by f(x) = x3 

Let x13 = x23

∴ x13 – x23 = 0

∴ `(x_1 - x_2) underbrace((x_1^2 + x_1 x_2 + x_2^2))_(> 0  "for all"  "x"_1,  "x"_2  "as it's discriminant" < 0)` = 0

∴ x1 = x2

∴ f is injective.

Let y = x3

∴ x = `y^(1/3)`

∴ For every y ∈ R, there is some x ∈ R

∴ f is surjective.

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पाठ 6: Functions - Exercise 6.1 [पृष्ठ ११९]

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