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Marcus tried to solve the differential equation 
(dy)/(dx)=(1)/(3x^(2)y^(2)). This is his work:

(dy)/(dx)=(1)/(3x^(2)y^(2))
Step 1: 
quad int3y^(2)dy=int(1)/(x^(2))dx
Step 2: 
quady^(3)=-(1)/(x)+C
Step 3: 
quad y=+-root(3)(-(1)/(x)+C)
Is Marcus's work correct? If not, what is his mistake?
Choose 1 answer:
(A) Marcus's work is correct.
(B) Step 2 is incorrect. Marcus didn't integrate 
3y^(2) correctly.
(C) Step 3 is incorrect. Marcus forgot to add a constant to the right-hand side at the end of the process.
(D) Step 3 is incorrect. The right-hand side of the equation should be 
root(3)(-(1)/(x)+C).

Marcus tried to solve the differential equation dydx=13x2y2 \frac{d y}{d x}=\frac{1}{3 x^{2} y^{2}} . This is his work:\newlinedydx=13x2y2 \frac{d y}{d x}=\frac{1}{3 x^{2} y^{2}} \newlineStep 11: 3y2dy=1x2dx \quad \int 3 y^{2} d y=\int \frac{1}{x^{2}} d x \newlineStep 22: y3=1x+C \quad y^{3}=-\frac{1}{x}+C \newlineStep 33: y=±1x+C3 \quad y= \pm \sqrt[3]{-\frac{1}{x}+C} \newlineIs Marcus's work correct? If not, what is his mistake?\newlineChoose 11 answer:\newline(A) Marcus's work is correct.\newline(B) Step 22 is incorrect. Marcus didn't integrate 3y2 3 y^{2} correctly.\newline(C) Step 33 is incorrect. Marcus forgot to add a constant to the right-hand side at the end of the process.\newline(D) Step 33 is incorrect. The right-hand side of the equation should be 1x+C3 \sqrt[3]{-\frac{1}{x}+C} .

Full solution

Q. Marcus tried to solve the differential equation dydx=13x2y2 \frac{d y}{d x}=\frac{1}{3 x^{2} y^{2}} . This is his work:\newlinedydx=13x2y2 \frac{d y}{d x}=\frac{1}{3 x^{2} y^{2}} \newlineStep 11: 3y2dy=1x2dx \quad \int 3 y^{2} d y=\int \frac{1}{x^{2}} d x \newlineStep 22: y3=1x+C \quad y^{3}=-\frac{1}{x}+C \newlineStep 33: y=±1x+C3 \quad y= \pm \sqrt[3]{-\frac{1}{x}+C} \newlineIs Marcus's work correct? If not, what is his mistake?\newlineChoose 11 answer:\newline(A) Marcus's work is correct.\newline(B) Step 22 is incorrect. Marcus didn't integrate 3y2 3 y^{2} correctly.\newline(C) Step 33 is incorrect. Marcus forgot to add a constant to the right-hand side at the end of the process.\newline(D) Step 33 is incorrect. The right-hand side of the equation should be 1x+C3 \sqrt[3]{-\frac{1}{x}+C} .
  1. Separate and Integrate Variables: Marcus starts by separating variables and integrating both sides of the differential equation.\newlinedydx=13x2y2\frac{dy}{dx} = \frac{1}{3x^{2}y^{2}}\newlineMultiplying both sides by dx and 3y23y^2 gives:\newline3y2dy=1x2dx3y^2 dy = \frac{1}{x^2} dx\newlineNow, integrate both sides:\newline3y2dy=1x2dx\int 3y^2 dy = \int \frac{1}{x^2} dx
  2. Multiply and Integrate: Marcus integrates both sides of the equation.\newlineThe integral of 3y23y^2 with respect to yy is y3y^3, not 3y33y^3, because the integral of aynay^n with respect to yy is (a/(n+1))y(n+1)(a/(n+1))y^{(n+1)} when n1n \neq -1.\newlineSo, 3y2dy=y3+C1\int 3y^2 \, dy = y^3 + C_1, where C1C_1 is the constant of integration.\newlineOn the right side, the integral of yy00 with respect to yy11 is yy22, where yy33 is the constant of integration.\newlineTherefore, the correct integration should be:\newlineyy44

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