<item ident="S1-6995" title="S1 | Phase Planes | ver. 6995"> <itemmetadata> <qtimetadata> <qtimetadatafield> <fieldlabel>question_type</fieldlabel> <fieldentry>essay_question</fieldentry> </qtimetadatafield> </qtimetadata> </itemmetadata> <presentation> <material> <mattextxml> <div class="exercise-statement"> <p> <strong>S1.</strong> </p> <p> Draw a phase plane for the following system of ODEs. </p> <p style="text-align:center;"> <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?x'= -2 \, x - 2 \, y" alt="x'= -2 \, x - 2 \, y" title="x'= -2 \, x - 2 \, y" data-latex="x'= -2 \, x - 2 \, y"/> </p> <p style="text-align:center;"> <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?y'= -4 \, x + 2 \, y + 18" alt="y'= -4 \, x + 2 \, y + 18" title="y'= -4 \, x + 2 \, y + 18" data-latex="y'= -4 \, x + 2 \, y + 18"/> </p> <p>Be sure to include and label the following features in your sketch:</p> <ul> <li>The isoclines <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?x'=0" alt="x'=0" title="x'=0" data-latex="x'=0"/> and <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?y'=0" alt="y'=0" title="y'=0" data-latex="y'=0"/>.</li> <li>Arrow systems describing trajectories of solutions.</li> <li>The equillibrium of the system.</li> </ul> </div> </mattextxml> <mattext texttype="text/html"><div class="exercise-statement"> <p> <strong>S1.</strong> </p> <p> Draw a phase plane for the following system of ODEs. </p> <p style="text-align:center;"> <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?x'=%20-2%20%5C,%20x%20-%202%20%5C,%20y" alt="x'= -2 \, x - 2 \, y" title="x'= -2 \, x - 2 \, y" data-latex="x'= -2 \, x - 2 \, y"> </p> <p style="text-align:center;"> <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?y'=%20-4%20%5C,%20x%20+%202%20%5C,%20y%20+%2018" alt="y'= -4 \, x + 2 \, y + 18" title="y'= -4 \, x + 2 \, y + 18" data-latex="y'= -4 \, x + 2 \, y + 18"> </p> <p>Be sure to include and label the following features in your sketch:</p> <ul> <li>The isoclines <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?x'=0" alt="x'=0" title="x'=0" data-latex="x'=0"> and <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?y'=0" alt="y'=0" title="y'=0" data-latex="y'=0">.</li> <li>Arrow systems describing trajectories of solutions.</li> <li>The equillibrium of the system.</li> </ul> </div> </mattext> </material> <response_str ident="response1" rcardinality="Single"> <render_fib> <response_label ident="answer1" rshuffle="No"/> </render_fib> </response_str> </presentation> <itemfeedback ident="general_fb"> <flow_mat> <material> <mattextxml> <div class="exercise-answer"> <h4>Partial Answer:</h4> <p> The isoclines cross at the equillibrium <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?\left(3, -3\right)" alt="\left(3, -3\right)" title="\left(3, -3\right)" data-latex="\left(3, -3\right)"/>, with <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?x'=0" alt="x'=0" title="x'=0" data-latex="x'=0"/> having a negative slope and <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?y'=0" alt="y'=0" title="y'=0" data-latex="y'=0"/> having a positive slope. </p> <p> The right region has a southwest arrow system, the top region has a northwest arrow system, the left region has a northeast arrow system, and the bottom region has a southeast arrow system. </p> </div> </mattextxml> <mattext texttype="text/html"><div class="exercise-answer"> <h4>Partial Answer:</h4> <p> The isoclines cross at the equillibrium <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?%5Cleft(3,%20-3%5Cright)" alt="\left(3, -3\right)" title="\left(3, -3\right)" data-latex="\left(3, -3\right)">, with <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?x'=0" alt="x'=0" title="x'=0" data-latex="x'=0"> having a negative slope and <img style="border:1px #ddd solid;padding:5px;border-radius:5px;" src="https://latex.codecogs.com/svg.latex?y'=0" alt="y'=0" title="y'=0" data-latex="y'=0"> having a positive slope. </p> <p> The right region has a southwest arrow system, the top region has a northwest arrow system, the left region has a northeast arrow system, and the bottom region has a southeast arrow system. </p> </div> </mattext> </material> </flow_mat> </itemfeedback> </item>