Question

y = 2x² - kx + 5. find the value of k if = dy/dx=8 at x = 2
Options
1. 16
2. 8
3. 4
4. 0
place answer fast ​

Answer 1

Answer:

differentiating we get

Explanation:

4x - k

since dy/dx = 8

4x - k = 8

4(2) - k = 8

k = 0

Answer 2

GiveN :

• y = 2x² - kx + 5
• dy/dx = 8 at x = 2

To FinD :

• Value of k

SolutioN :

Take Given equation :

$\longrightarrow \sf{y \: = \: 2x^2 \: - \: kx \: + \: 5} \\ \\ {\small{\sf{ \: \: \: \: \: \: \: \: Differentiate \: wrt. \: x}}} \\ \\ \longrightarrow \sf{\dfrac{dy}{dx} \: = \: \dfrac{d(2x^2 \: - \: kx \: + \: 4)}{dx}} \\ \\ \longrightarrow \sf{\dfrac{dy}{dx} \: = \: 2(2x) \: - \: k \: + \: 0} \\ \\ \longrightarrow \sf{\dfrac{dy}{dx} \: = \: 4x \: - \: k}$

Now, put value of dy/dx and at x = 2

So,

$\longrightarrow \sf{8 \: = \: 4x \: - \: k} \\ \\ \longrightarrow \sf{8 \: = \: 4(2) \: - \: k} \\ \\ \longrightarrow \sf{8 \: = \: 8 \: - \: k} \\ \\ \longrightarrow \sf{-k \: = \: 8 \: - \: 8} \\ \\ \longrightarrow \sf{-k \: = \: 0} \\ \\ \: \: \: \: \: \: \: \: \: \: \: \: \: \Large{\underline{\boxed{\sf{k \: = \: 0}}}}$