<item ident="S1-7357" title="S1 | Phase Planes | ver. 7357"> <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'= 4 \, x + 4 \, y + 4" alt="x'= 4 \, x + 4 \, y + 4" title="x'= 4 \, x + 4 \, y + 4" data-latex="x'= 4 \, x + 4 \, y + 4"/> </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 - 5 \, y + 13" alt="y'= 4 \, x - 5 \, y + 13" title="y'= 4 \, x - 5 \, y + 13" data-latex="y'= 4 \, x - 5 \, y + 13"/> </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'=%204%20%5C,%20x%20+%204%20%5C,%20y%20+%204" alt="x'= 4 \, x + 4 \, y + 4" title="x'= 4 \, x + 4 \, y + 4" data-latex="x'= 4 \, x + 4 \, y + 4"> </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'=%204%20%5C,%20x%20-%205%20%5C,%20y%20+%2013" alt="y'= 4 \, x - 5 \, y + 13" title="y'= 4 \, x - 5 \, y + 13" data-latex="y'= 4 \, x - 5 \, y + 13"> </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(-2, 1\right)" alt="\left(-2, 1\right)" title="\left(-2, 1\right)" data-latex="\left(-2, 1\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 northeast arrow system, the top region has a southeast arrow system, the left region has a southwest arrow system, and the bottom region has a northwest 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(-2,%201%5Cright)" alt="\left(-2, 1\right)" title="\left(-2, 1\right)" data-latex="\left(-2, 1\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 northeast arrow system, the top region has a southeast arrow system, the left region has a southwest arrow system, and the bottom region has a northwest arrow system. </p> </div> </mattext> </material> </flow_mat> </itemfeedback> </item>