Math Problem Statement

If 2xy + 3 = 5x^2, then x * (d²y/dx²) + 2 * (dy/dx) = ?

Solution

The given equation is:

2xy+3=5x22xy + 3 = 5x^2

We are asked to find xd2ydx2+2dydxx \frac{d^2 y}{dx^2} + 2 \frac{dy}{dx}.

Step 1: Implicit Differentiation

First, let's differentiate the equation 2xy+3=5x22xy + 3 = 5x^2 implicitly with respect to xx.

First derivative:

ddx(2xy+3)=ddx(5x2)\frac{d}{dx} (2xy + 3) = \frac{d}{dx} (5x^2) Applying the product rule on 2xy2xy, we get: 2(y+xdydx)=10x2 \left( y + x \frac{dy}{dx} \right) = 10x Simplifying, we get: 2y+2xdydx=10x2y + 2x \frac{dy}{dx} = 10x y+xdydx=5xy + x \frac{dy}{dx} = 5x

Second derivative:

Now, let's differentiate the equation y+xdydx=5xy + x \frac{dy}{dx} = 5x again with respect to xx.

ddx(y+xdydx)=ddx(5x)\frac{d}{dx} \left( y + x \frac{dy}{dx} \right) = \frac{d}{dx} (5x) Applying the product rule again on xdydxx \frac{dy}{dx}, we get: dydx+(dydx+xd2ydx2)=5\frac{dy}{dx} + \left( \frac{dy}{dx} + x \frac{d^2 y}{dx^2} \right) = 5 Simplifying: 2dydx+xd2ydx2=52 \frac{dy}{dx} + x \frac{d^2 y}{dx^2} = 5

Step 2: Rearrange the equation

The expression xd2ydx2+2dydxx \frac{d^2 y}{dx^2} + 2 \frac{dy}{dx} is already simplified, and it equals:

xd2ydx2+2dydx=5x \frac{d^2 y}{dx^2} + 2 \frac{dy}{dx} = 5

Thus, the final result is:

xd2ydx2+2dydx=5x \frac{d^2 y}{dx^2} + 2 \frac{dy}{dx} = 5

Would you like a detailed explanation of any step?


Here are 5 related questions you might find helpful:

  1. What is implicit differentiation, and how is it used?
  2. Can we solve for yy explicitly in terms of xx from the original equation?
  3. What are some applications of second-order derivatives in real-world problems?
  4. How do product and chain rules help in differentiation of composite functions?
  5. Can you derive the second derivative from different types of implicit functions?

Tip: Always double-check when applying the product rule in differentiation, especially when variables are multiplied.

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Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Second-Order Derivatives
Product Rule
Algebraic Equation

Formulas

d/dx (2xy + 3) = d/dx (5x^2)
Product Rule: d/dx (u * v) = u'v + uv'
Second derivative: d²y/dx²

Theorems

Product Rule
Chain Rule

Suitable Grade Level

Grades 11-12 or Early College Level