<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 z=f(x,y)=(x+y)(xy+xy^{2})}"><semantics><mrow class="MJX-TeXAtom-ORD"><mstyle displaystyle="true" scriptlevel="0"><mi>z</mi><mo>=</mo><mi>f</mi><mo stretchy="false">(</mo><mi>x</mi><mo>,</mo><mi>y</mi><mo stretchy="false">)</mo><mo>=</mo><mo stretchy="false">(</mo><mi>x</mi><mo>+</mo><mi>y</mi><mo stretchy="false">)</mo><mo stretchy="false">(</mo><mi>x</mi><mi>y</mi><mo>+</mo><mi>x</mi><msup><mi>y</mi><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msup><mo stretchy="false">)</mo></mstyle></mrow><annotation encoding="application/x-tex">{\displaystyle z=f(x,y)=(x+y)(xy+xy^{2})}</annotation></semantics></math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/a93b41edadf3abc10ae9960f051a262a80a16f4b" class="mwe-math-fallback-image-inline" aria-hidden="true" style="vertical-align: -0.838ex; width:31.706ex; height:3.176ex;" alt="{\displaystyle z=f(x,y)=(x+y)(xy+xy^{2})}"></span>
<a href="//commons.wikimedia.org/wiki/User:Kmhkmh" title="User:Kmhkmh">Kmhkmh</a>
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