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+1 vote
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in Sets, relations and functions by (20 points)
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\(f(x)= \frac{3x^2}{4\pi}-cos\pi x\)

Find f(x) is one-one or many-one and onto or into.

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1 Answer

+1 vote
by (710 points)

f(x) \(=\frac{3\mathrm x^2}{4\pi}\) – cos πx

\(\because\) f(x) \(=\frac{3\mathrm x^2}{4\pi}\) – cos πx

And f(–x) \(=\frac{3\mathrm x^2}{4\pi}\) – cos(–πx)

\(=\frac{3\mathrm x^2}{4\pi}\) – cos πx (\(\because\) cos(–θ) = cos θ)

Therefore, f(x) = f(–x)

Hence, f is not one-one function.

\(\therefore\) f is many-one function.

Now, Range of \(\frac{3\mathrm x^2}{4\pi}\) is [0, \(\infty\)]

and Range of cos πx = [–1, 1]

Therefore, the range of f(x) is [–1, \(\infty\)).

\(\therefore\) f(x) never gets negative values less than 1.

Hence, f(x) is not onto  (\(\because\) Domain of f(x) is R)

Therefore, f(x) is into function.

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