Bytelearn - cat image with glassesAI tutor

Welcome to Bytelearn!

Let’s check out your problem:

Lara tried to solve the differential equation 
(dy)/(dx)=xy+2x. This is her work:

(dy)/(dx)=xy+2x
Step 1:

(dy)/(dx)=x(y+2)
Step 2: 
quad int(y+2)^(-1)dy=int xdx
Step 3: 
quad ln |y+2|=(x^(2))/(2)+C_(1)
Step 4: 
quade^(ln |y+2|)=e^((x^(2))/(2)+C_(1))
Step 5: 
quad|y+2|=e^((x^(2))/(2))e^(C_(1))
Step 6: 
quad y+2=Ce^((x^(2))/(2))
Step 7:

y=Ce^((x^(2))/(2))-2
Is Lara's work correct? If not, what is her mistake?
Choose 1 answer:
(A) Lara's work is correct.
(B) Step 1 is incorrect. We're not allowed to factor an expression when solving differential equations.
(C) Step 
2 is incorrect. The separation of variables wasn't done correctly.
(D) Step 4 is incorrect. The right-hand side of the equation should be 
e^((z^(2))/(2))+C_(1).

Lara tried to solve the differential equation dydx=xy+2x \frac{d y}{d x}=x y+2 x . This is her work:\newlinedydx=xy+2x \frac{d y}{d x}=x y+2 x \newlineStep 11: dydx=x(y+2)\quad \frac{d y}{d x}=x(y+2) \newlineStep 22: (y+2)1dy=xdx \quad \int(y+2)^{-1} d y=\int x d x \newlineStep 33: lny+2=x22+C1 \quad \ln |y+2|=\frac{x^{2}}{2}+C_{1} \newlineStep 44: elny+2=ex22+C1 \quad e^{\ln |y+2|}=e^{\frac{x^{2}}{2}+C_{1}} \newlineStep 55: y+2=ex22eC1 \quad|y+2|=e^{\frac{x^{2}}{2}} e^{C_{1}} \newlineStep 66: y+2=Cex22 \quad y+2=C e^{\frac{x^{2}}{2}} \newlineStep 77: y=Cex222\quad y=C e^{\frac{x^{2}}{2}}-2 \newlineIs Lara's work correct? If not, what is her mistake?\newlineChoose 11 answer:\newline(A) Lara's work is correct.\newline(B) Step 11 is incorrect. We're not allowed to factor an expression when solving differential equations.\newline(C) Step 2 \mathbf{2} is incorrect. The separation of variables wasn't done correctly.\newline(D) Step 44 is incorrect. The right-hand side of the equation should be ez22+C1 e^{\frac{z^{2}}{2}}+C_{1} .

Full solution

Q. Lara tried to solve the differential equation dydx=xy+2x \frac{d y}{d x}=x y+2 x . This is her work:\newlinedydx=xy+2x \frac{d y}{d x}=x y+2 x \newlineStep 11: dydx=x(y+2)\quad \frac{d y}{d x}=x(y+2) \newlineStep 22: (y+2)1dy=xdx \quad \int(y+2)^{-1} d y=\int x d x \newlineStep 33: lny+2=x22+C1 \quad \ln |y+2|=\frac{x^{2}}{2}+C_{1} \newlineStep 44: elny+2=ex22+C1 \quad e^{\ln |y+2|}=e^{\frac{x^{2}}{2}+C_{1}} \newlineStep 55: y+2=ex22eC1 \quad|y+2|=e^{\frac{x^{2}}{2}} e^{C_{1}} \newlineStep 66: y+2=Cex22 \quad y+2=C e^{\frac{x^{2}}{2}} \newlineStep 77: y=Cex222\quad y=C e^{\frac{x^{2}}{2}}-2 \newlineIs Lara's work correct? If not, what is her mistake?\newlineChoose 11 answer:\newline(A) Lara's work is correct.\newline(B) Step 11 is incorrect. We're not allowed to factor an expression when solving differential equations.\newline(C) Step 2 \mathbf{2} is incorrect. The separation of variables wasn't done correctly.\newline(D) Step 44 is incorrect. The right-hand side of the equation should be ez22+C1 e^{\frac{z^{2}}{2}}+C_{1} .
  1. Factor out x: Lara's initial equation is (dydx=xy+2x)(\frac{dy}{dx} = xy + 2x). Step 11: She factors out x from the right-hand side to get (dydx=x(y+2))(\frac{dy}{dx} = x(y + 2)).
  2. Separate variables: Lara attempts to separate variables by writing (y+2)1dy=xdx\int(y + 2)^{-1}\,dy = \int x\,dx.
  3. Integrate both sides: She integrates both sides to get lny+2=x22+C1\ln|y + 2| = \frac{x^2}{2} + C_1.
  4. Exponentiate both sides: Lara exponentiates both sides to remove the natural logarithm, writing elny+2=e(x22)+C1e^{\ln|y + 2|} = e^{\left(\frac{x^2}{2}\right) + C_1}.
  5. Simplify expressions: She simplifies the left-hand side to y+2|y + 2| and the right-hand side to e(x2)/2eC1e^{(x^2)/2}e^{C_1}.
  6. Find general constant: Lara writes y+2=Cex22y + 2 = Ce^{\frac{x^2}{2}}, where C=eC1C = e^{C_1} is the general constant.
  7. Solve for y: She solves for y to get y=Cex2/22y = Ce^{x^2/2} - 2.

More problems from Solve linear equations with variables on both sides: word problems