Directions : In the following questions, A statement of Assertion (A)...
f(x) = x3 - 3x2+ 6x - 100
f(x) = 3x2 - 6x + 6
= 3[x2 - 2x + 2]
= 3[(x-1)2+1]
Since f’(x) > 0; x ∊ R
f(x) is strictly increasing on R.
Hence A is true.
For a strictly increasing function,
x1 > x2⇒ f(x1) > f(x2)
i.e.) x1 = x2
⇒ f(x1) — f(x2)
Hence, a strictly increasing function is always an injective function.
So R is true.
But R is not the correct explanation of A.
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Directions : In the following questions, A statement of Assertion (A)...
Assertion (A): The function f(x) = x^3 – 3x^2 + 6x – 100 is strictly increasing on the set of real numbers.
Reason (R): A strictly increasing function is an injective function.
To determine whether Assertion (A) and Reason (R) are true or false, we need to analyze each statement separately.
Analysis of Assertion (A):
To check whether the function f(x) = x^3 – 3x^2 + 6x – 100 is strictly increasing, we need to examine the sign of its derivative. If the derivative is positive for all values of x, then the function is strictly increasing.
Taking the derivative of f(x), we get:
f'(x) = 3x^2 – 6x + 6
To find the critical points of the function, we set f'(x) = 0:
3x^2 – 6x + 6 = 0
Using the quadratic formula, we get:
x = (6 ± √(6^2 - 4(3)(6))) / (2(3))
x = (6 ± √(36 - 72)) / 6
x = (6 ± √(-36)) / 6
x = (6 ± 6i√(1)) / 6
x = 1 ± i
Since the derivative does not equal zero for any real value of x, there are no critical points. Therefore, the derivative is always positive, indicating that the function is strictly increasing on the set of real numbers.
Analysis of Reason (R):
The reason states that a strictly increasing function is an injective function. This is true because if a function is strictly increasing, it means that for any two distinct input values x1 and x2, the corresponding output values f(x1) and f(x2) will also be distinct. In other words, the function does not map different inputs to the same output, making it injective.
Conclusion:
Both Assertion (A) and Reason (R) are true. Furthermore, Reason (R) correctly explains Assertion (A) because a strictly increasing function is indeed an injective function. Therefore, option B is the correct answer.