Math  /  Calculus

Question7. Find dydx\frac{d y}{d x} if y23xy+x2=7y^{2}-3 x y+x^{2}=7. (a) 2x+y3x2y\frac{2 x+y}{3 x-2 y} (b) 3y2x2y3x\frac{3 y-2 x}{2 y-3 x} (c) 2x32y\frac{2 x}{3-2 y} (d) 2xy\frac{2 x}{y} (e) None of these

Studdy Solution

STEP 1

What is this asking? We need to find the derivative of yy with respect to xx, written as dydx\frac{dy}{dx}, given the equation y23xy+x2=7y^2 - 3xy + x^2 = 7. Watch out! Remember that yy is a function of xx, so we'll need to use the chain rule when differentiating terms involving yy.
Don't forget to treat yy as y(x)y(x)!

STEP 2

1. Implicit Differentiation
2. Isolate and Simplify

STEP 3

Let's **differentiate** both sides of the equation y23xy+x2=7y^2 - 3xy + x^2 = 7 with respect to xx.
Remember, we're thinking of yy as a function of xx, so we'll need the **chain rule** for terms involving yy.

STEP 4

ddx(y2)ddx(3xy)+ddx(x2)=ddx(7) \frac{d}{dx}(y^2) - \frac{d}{dx}(3xy) + \frac{d}{dx}(x^2) = \frac{d}{dx}(7) 2ydydx(3y+3xdydx)+2x=0 2y \cdot \frac{dy}{dx} - \left( 3y + 3x \cdot \frac{dy}{dx} \right) + 2x = 0 Here, we used the **power rule** and **chain rule** on y2y^2 to get 2ydydx2y \cdot \frac{dy}{dx}.
We used the **product rule** on 3xy3xy to get 3y+3xdydx3y + 3x \cdot \frac{dy}{dx}.
And the **power rule** on x2x^2 gives us 2x2x.
The derivative of the constant 77 is just **zero**.

STEP 5

Now, let's **isolate** dydx\frac{dy}{dx} terms on one side and everything else on the other: 2ydydx3xdydx=3y2x 2y \cdot \frac{dy}{dx} - 3x \cdot \frac{dy}{dx} = 3y - 2x

STEP 6

We can **factor out** dydx\frac{dy}{dx}: dydx(2y3x)=3y2x \frac{dy}{dx}(2y - 3x) = 3y - 2x

STEP 7

Finally, we **divide** both sides by (2y3x)(2y - 3x) to solve for dydx\frac{dy}{dx}: dydx=3y2x2y3x \frac{dy}{dx} = \frac{3y - 2x}{2y - 3x}

STEP 8

So, our **final answer** is dydx=3y2x2y3x\frac{dy}{dx} = \frac{3y - 2x}{2y - 3x}, which matches option (b)!

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