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If $$y = y(x)$$ is the solution of the differential equation, $$x\frac{dy}{dx} + 2y = x^2$$ satisfying $$y(1) = 1$$, then $$y\left(\frac{1}{2}\right)$$ is equal to:
We start with the given differential equation $$x\dfrac{dy}{dx}+2y = x^{2}.$$
To bring it to the standard linear form $$\dfrac{dy}{dx}+P(x)\,y = Q(x),$$ we divide every term by $$x$$ (note that we are looking around $$x>0$$, so division is legitimate):
$$\dfrac{dy}{dx} + \dfrac{2}{x}\,y = x.$$
Here we can clearly read $$P(x)=\dfrac{2}{x}$$ and $$Q(x)=x.$$
For a first-order linear differential equation, the integrating factor (I.F.) is defined by the formula
$$\text{I.F.}=e^{\displaystyle\int P(x)\,dx}.$$
Substituting $$P(x)=\dfrac{2}{x},$$ we obtain
$$\text{I.F.}=e^{\displaystyle\int \frac{2}{x}\,dx}=e^{2\ln|x|}=|x|^{2}=x^{2}$$
(we use $$x>0$$ so $$|x|=x$$).
Now we multiply the whole differential equation in its linear form by this integrating factor:
$$x^{2}\left(\dfrac{dy}{dx}\right)+x^{2}\left(\dfrac{2}{x}\right)y = x^{2}\cdot x.$$
Performing the obvious simplifications, we get
$$x^{2}\dfrac{dy}{dx}+2x\,y = x^{3}.$$
The left-hand side is the exact derivative of the product $$y\,(x^{2})$$ because of the rule $$\dfrac{d}{dx}\bigl(y\cdot x^{2}\bigr)=x^{2}\dfrac{dy}{dx}+2x\,y.$$ Hence we can rewrite the equation compactly as
$$\dfrac{d}{dx}\Bigl(y\,x^{2}\Bigr)=x^{3}.$$
We integrate both sides with respect to $$x$$:
$$\int\dfrac{d}{dx}\Bigl(y\,x^{2}\Bigr)\,dx=\int x^{3}\,dx.$$
On integration, the left side simply gives back the function inside the derivative, while the right side yields $$\dfrac{x^{4}}{4}+C,$$ where $$C$$ is the constant of integration. Thus,
$$y\,x^{2}= \dfrac{x^{4}}{4}+C.$$
We now solve for $$y$$ by dividing by $$x^{2}$$:
$$y=\dfrac{x^{4}}{4x^{2}}+\dfrac{C}{x^{2}}=\dfrac{x^{2}}{4}+\dfrac{C}{x^{2}}.$$
To determine the constant $$C,$$ we use the initial condition $$y(1)=1.$$ Substituting $$x=1,\,y=1$$ in the general solution, we obtain
$$1=\dfrac{(1)^{2}}{4}+\dfrac{C}{(1)^{2}}=\dfrac{1}{4}+C.$$
Hence, $$C=1-\dfrac{1}{4}=\dfrac{3}{4}.$$
Substituting this value of $$C$$ back into the expression for $$y,$$ we get the particular solution
$$y(x)=\dfrac{x^{2}}{4}+\dfrac{\tfrac{3}{4}}{x^{2}}=\dfrac{x^{2}}{4}+\dfrac{3}{4x^{2}}.$$
Now we evaluate $$y\!\left(\dfrac{1}{2}\right).$$ First compute $$x^{2}$$ when $$x=\dfrac{1}{2}:$$
$$x^{2}=\left(\dfrac{1}{2}\right)^{2}=\dfrac{1}{4}.$$
Substituting into the formula for $$y$$, we have
$$y\!\left(\dfrac{1}{2}\right)=\dfrac{\dfrac{1}{4}}{4}+\dfrac{3}{4\left(\dfrac{1}{2}\right)^{2}}=\dfrac{1}{16}+\dfrac{3}{4\cdot\dfrac{1}{4}}.$$
Because $$4\left(\dfrac{1}{2}\right)^{2}=4\cdot\dfrac{1}{4}=1,$$ the denominator of the second term is $$1,$$ so that term simplifies straightaway to $$3.$$
Thus
$$y\!\left(\dfrac{1}{2}\right)=\dfrac{1}{16}+3=\dfrac{1}{16}+\dfrac{48}{16}=\dfrac{49}{16}.$$
Hence, the correct answer is Option D.
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