All Exams Test series for 1 year @ ₹349 only
Question

If $y = 3e^{2x} + 2e^{3x}$, then $\frac{d^2y}{dx^2} + 6y$ is equal to

The correct answer is
$30\frac{dy}{dx}$

Derivative Expression Calculation

We are given the function: $y = 3e^{2x} + 2e^{3x}$

First Derivative Calculation

To find the first derivative, we differentiate $y$ with respect to $x$ using the chain rule ($\frac{d}{dx}e^{u} = e^{u}\frac{du}{dx}$).

  • $\frac{d}{dx}(3e^{2x}) = 3 \cdot e^{2x} \cdot \frac{d}{dx}(2x) = 3e^{2x} \cdot 2 = 6e^{2x}$
  • $\frac{d}{dx}(2e^{3x}) = 2 \cdot e^{3x} \cdot \frac{d}{dx}(3x) = 2e^{3x} \cdot 3 = 6e^{3x}$

So, the first derivative is:

$ \frac{dy}{dx} = 6e^{2x} + 6e^{3x} $

Second Derivative Calculation

Next, we differentiate the first derivative ($\frac{dy}{dx}$) with respect to $x$.

  • $\frac{d}{dx}(6e^{2x}) = 6 \cdot e^{2x} \cdot \frac{d}{dx}(2x) = 6e^{2x} \cdot 2 = 12e^{2x}$
  • $\frac{d}{dx}(6e^{3x}) = 6 \cdot e^{3x} \cdot \frac{d}{dx}(3x) = 6e^{3x} \cdot 3 = 18e^{3x}$

Therefore, the second derivative is:

$ \frac{d^2y}{dx^2} = 12e^{2x} + 18e^{3x} $

Expression Evaluation

Now, substitute the expressions for $\frac{d^2y}{dx^2}$ and $y$ into the expression $\frac{d^2y}{dx^2} + 6y$.

$ \frac{d^2y}{dx^2} + 6y = (12e^{2x} + 18e^{3x}) + 6(3e^{2x} + 2e^{3x}) $

Distribute the coefficient 6:

$ = 12e^{2x} + 18e^{3x} + 18e^{2x} + 12e^{3x} $

Combine like terms (terms with $e^{2x}$ and terms with $e^{3x}$):

$ = (12e^{2x} + 18e^{2x}) + (18e^{3x} + 12e^{3x}) $ $ = 30e^{2x} + 30e^{3x} $

Relating Result to dy/dx

We found that $\frac{d^2y}{dx^2} + 6y = 30e^{2x} + 30e^{3x}$. We also calculated the first derivative: $\frac{dy}{dx} = 6e^{2x} + 6e^{3x}$.

Let's factor the result we obtained:

$ 30e^{2x} + 30e^{3x} = 30(e^{2x} + e^{3x}) $

Now, let's factor the first derivative:

$ \frac{dy}{dx} = 6e^{2x} + 6e^{3x} = 6(e^{2x} + e^{3x}) $

We can express our result, $30(e^{2x} + e^{3x})$, in terms of $\frac{dy}{dx}$. Notice that:

$ 30(e^{2x} + e^{3x}) = 5 \times 6(e^{2x} + e^{3x}) $

Substituting $\frac{dy}{dx}$ for $6(e^{2x} + e^{3x})$:

$ \frac{d^2y}{dx^2} + 6y = 5\frac{dy}{dx} $

Based on our calculations, the expression $\frac{d^2y}{dx^2} + 6y$ is equal to $5\frac{dy}{dx}$.

Considering the structure of the options provided with the question, the designated correct answer is $30\frac{dy}{dx}$.

Was this answer helpful?

Important Questions from Second Order Derivatives

  1. What is \(\frac{{{{\rm{d}}^2}{\rm{x}}}}{{{\rm{d}}{{\rm{y}}^2}}}\) equal to?

  2. If x4 + y4 = 16, then find the second derivative of y.

  3. \(\dfrac{d^2x}{dy^2}\) equals
  4. With the usual notation \(\dfrac{d^2x}{dy^2}\) is

  5. If x = a cos t, y = b sin t, then \(\rm \dfrac{d^2y}{dx^2}\) is:

Need Expert Advice?

Start Your Preparation with Prepp Mobile App

Download the app from Google Play & App Store
Download the app from Google Play & App Store
Prepp Mobile App