A plot of the vector field <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle F(x,y)=-x^{2}{\boldsymbol {\hat {y}}}}"><semantics><mrow class="MJX-TeXAtom-ORD"><mstyle displaystyle="true" scriptlevel="0"><mi>F</mi><mo stretchy="false">(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo stretchy="false">)</mo><mo>=</mo><mo>−<!-- − --></mo><msup><mi>x</mi><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msup><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><mover><mi mathvariant="bold-italic">y</mi><mo mathvariant="bold" stretchy="false">^<!-- ^ --></mo></mover></mrow></mrow></mstyle></mrow><annotation encoding="application/x-tex">{\displaystyle F(x,y)=-x^{2}{\boldsymbol {\hat {y}}}}</annotation></semantics></math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/5bc5424e37823b68d91bb0f7ad5c17fe2331cf35" class="mwe-math-fallback-image-inline" aria-hidden="true" style="vertical-align: -0.838ex; width:15.862ex; height:3.176ex;" alt="{\displaystyle F(x,y)=-x^{2}{\boldsymbol {\hat {y}}}}"></span>. 
Self-made with Mathematica 7.0
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