Q. If −2x2+y2+y3+3x=0 then find dxdy at the point (2,1).Answer: dxdy∣∣(2,1)=
Apply Implicit Differentiation: To find the derivative of y with respect to x, dxdy, for the given equation, we need to use implicit differentiation because y is not isolated on one side of the equation.
Differentiate Each Term: Differentiate both sides of the equation with respect to x, applying the chain rule where necessary. The equation is −2x2+y2+y3+3x=0.Differentiating term by term, we get:dxd(−2x2)+dxd(y2)+dxd(y3)+dxd(3x)=dxd(0)
Solve for (\frac{dy}{dx}): Differentiate each term:\(\newline\$\frac{d}{dx}(-2x^2) = -4x\)\(\newline\)\(\frac{d}{dx}(y^2) = 2y \cdot (\frac{dy}{dx})\) (using the chain rule)\(\newline\)\(\frac{d}{dx}(y^3) = 3y^2 \cdot (\frac{dy}{dx})\) (using the chain rule)\(\newline\)\(\frac{d}{dx}(3x) = 3\)\(\newline\)\(\frac{d}{dx}(0) = 0\)\(\newline\)So, we have \(-4x + 2y(\frac{dy}{dx}) + 3y^2(\frac{dy}{dx}) + 3 = 0\)
Factor Out \(\frac{dy}{dx}\): Now, we need to solve for \(\frac{dy}{dx}\). Group all the terms involving \(\frac{dy}{dx}\) on one side and the rest on the other side:\(\newline\)\(2y\frac{dy}{dx} + 3y^2\frac{dy}{dx} = 4x - 3\)
Isolate \(\frac{dy}{dx}\): Factor out \(\frac{dy}{dx}\) from the left side:\(\newline\)\(\frac{dy}{dx}(2y + 3y^2) = 4x - 3\)
Substitute Values: Divide both sides by \((2y + 3y^2)\) to isolate \((\frac{dy}{dx}):\)\[(\frac{dy}{dx}) = \frac{(4x - 3)}{(2y + 3y^2)}\]
Calculate \((\frac{dy}{dx}): Now we need to substitute \$x = 2\) and \(y = 1\) into the equation to find the value of \((\frac{dy}{dx})\) at the point \((2,1)\):\(\newline\)\((\frac{dy}{dx})|_{(\(2\),\(1\))} = \frac{(\(4\)(\(2\)) - \(3\))}{(\(2\)(\(1\)) + \(3\)(\(1\))^\(2\))}
Calculate \((\frac{dy}{dx}): Now we need to substitute \$x = 2\) and \(y = 1\) into the equation to find the value of \((\frac{dy}{dx})\) at the point \((2,1)\): \((\frac{dy}{dx})|_{(2,1)} = \frac{(4(2) - 3)}{(2(1) + 3(1)^2)}\)Calculate the value: \((\frac{dy}{dx})|_{(2,1)} = \frac{(8 - 3)}{(2 + 3)}\) \((\frac{dy}{dx})|_{(2,1)} = \frac{5}{5}\) \((\frac{dy}{dx})|_{(2,1)} = 1\)