Knowee
Questions
Features
Study Tools

If the function f(x) = kx3 - 9x2 + 9 x + 3 is monotonically increasing in every interval, then

Question

If the function f(x)=kx39x2+9x+3 f(x) = kx^3 - 9x^2 + 9 x + 3 is monotonically increasing in every interval, then

🧐 Not the exact question you are looking for?Go ask a question

Solution

To determine if the function is monotonically increasing in every interval, we need to find its derivative and set it greater than zero.

The derivative of the function f(x) = kx^3 - 9x^2 + 9x + 3 is f'(x) = 3kx^2 - 18x + 9.

Setting f'(x) > 0 gives us 3kx^2 - 18x + 9 > 0.

This is a quadratic inequality. To solve it, we first find the roots of the equation 3kx^2 - 18x + 9 = 0.

Using the quadratic formula, the roots are x = [18 ± sqrt((18)^2 - 43k9)] / (2*3k) = [18 ± sqrt(324 - 108k)] / 6k.

For the function to be monotonically increasing, the discriminant (the value under the square root) must be less than or equal to zero. This is because if the discriminant is greater than zero, the quadratic equation will have two distinct real roots, meaning the function will decrease between these roots.

So, we have 324 - 108k ≤ 0.

Solving this inequality gives us k ≥ 3.

Therefore, for the function f(x) = kx^3 - 9x^2 + 9x + 3 to be monotonically increasing in every interval, k must be greater than or equal to 3.

This problem has been solved

Similar Questions

Find the intervals in which the following function  f(x)=20−9x+6x2−x3𝑓𝑥=20−9𝑥+6𝑥2−𝑥3 is(a)𝑎 Strictly increasing,(b)𝑏 Strictly decreasing.

Find the open intervals on which the function 𝑓 is increasing or decreasing, and find the 𝑥-values of all relative extrema (turning points).𝑓(𝑥)=3⋅𝑥−𝑥3

Find the intervals on which the function is increasing and the intervals on which the function is decreasing.f(x) = -3x2 + 12x + 36

True or false?(a) The function f(x) = 3x + 9 has constant average rate of change on all intervals.

Function f(x)=2x3−9x2+12x+29𝑓𝑥=2𝑥3-9𝑥2+12𝑥+29 is decreasing when x∈(a, b)𝑥∈𝑎, 𝑏 then find value of a+b𝑎+𝑏.

1/1

Upgrade your grade with Knowee

Get personalized homework help. Review tough concepts in more detail, or go deeper into your topic by exploring other relevant questions.