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Let f:R→Rf : R \to R defined by f(x)=2x3−7f(x) = 2x^3 - 7 for x∈Rx \in R. Then :

(A) ff is one-one function

(B) ff is many to one function

(C) ff is bijective function

(D) ff is into function

Choose the correct answer from the options given below :

Solution

✅ Correct Option: 4

f′(x)=6x2≥0f'(x) = 6x^2 \geq 0, with equality only at x=0x=0, so ff is strictly increasing, hence one-one.

As x→±∞x \to \pm\infty, f→±∞f \to \pm\infty, so range is RR (onto).

Thus ff is bijective: (A) and (C).

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