// Numbas version: exam_results_page_options {"name": "Ausdr\u00fccke mit Quadratwurzeln vereinfachen", "extensions": [], "custom_part_types": [], "resources": [], "navigation": {"allowregen": true, "showfrontpage": false, "preventleave": false, "typeendtoleave": false}, "question_groups": [{"pickingStrategy": "all-ordered", "questions": [{"name": "Ausdr\u00fccke mit Quadratwurzeln vereinfachen", "tags": [], "metadata": {"description": "
Quadratwurzeln vereinfachen, Nenner rational machen
\nDeutsche Übersetzung von https://numbas.mathcentre.ac.uk/question/22587/using-surds-rationalising-the-denominator/ von Elliott Fletcher
", "licence": "Creative Commons Attribution 4.0 International"}, "statement": "Benutzen Sie sqrt()
, um eine Quadratwurzel einzugeben. Um zum Beispiel $\\sqrt{3}$ einzugeben, tippen Sie sqrt(3)
in dem Eingabefeld. Um zum Beispiel $3\\sqrt{5}$ einzugeben, tippen Sie 3*sqrt(5)
in das Eingabefeld.
Für nicht-negative reelle Zahlen $a$, $b$ gilt
\n\\[\\sqrt{ab} = \\sqrt{a} \\cdot \\sqrt{b}.\\]
\nEin Wurzelausdruck kann vereinfacht werden, wenn die Zahl unter der Wurzel als Produkt einer Quadratzahl $>1$ und einer weiteren Zahl geschrieben werden kann.
\nIn unserem Fall ist $\\var{p}$ eine Primzahl.
\nFolglich kann $\\sqrt{\\var{p}}$ nicht weiter vereinfacht werden.
\nGenauso ist $\\var{a}$ eine Primzahl, und $\\sqrt{\\var{a}}$ kann ebenfalls nicht weiter vereinfacht werden.
\nAndererseits können wir $\\simplify{{a}*{n}^2}$ als Produkt schreiben und $\\sqrt{\\simplify{{a}*{n}^2}}$ vereinfachen zu
\n\\[
\\begin{align}
\\sqrt{\\simplify{{a}*{n}^2}} &= \\sqrt{\\simplify{{n}^2}} \\cdot \\sqrt{\\var{a}}\\\\
&= \\simplify{{n}*sqrt({a})}.
\\end{align}
\\]
Mit demselben Wurzelgesetz wie in Teil a), lässt sich $\\sqrt{\\simplify{{n}^2*{p}}}$ vereinfachen zu
\n\\[
\\begin{align}
\\sqrt{\\simplify{{n}^2*{p}}} &= \\sqrt{\\simplify{{n}^2}} \\cdot \\sqrt{\\var{p}}\\\\
&= \\simplify{{n}*sqrt({p})}.
\\end{align}
\\]
In diesem Abschnitt benutzen wir die folgenden Regeln (für nicht-negative reelle Zahlen $a$, $b$; für die zweite Gleichheit muss $b\\ne 0$ gelten).
\n\\[\\sqrt{ab} = \\sqrt{a} \\cdot \\sqrt{b} \\text{.} \\]
\n\\[ \\sqrt{\\frac{a}{b}} = \\frac{\\sqrt{a}}{\\sqrt{b}} \\text{.} \\]
\nDamit vereinfachen wir $\\displaystyle\\frac{ \\sqrt{\\simplify{{a}*{v}}} }{ \\sqrt{\\var{a}} }$ wie folgt:
\n\\[
\\begin{align}
\\frac{\\sqrt{\\simplify{{a}*{v}}}}{\\sqrt{\\var{a}}} &= \\frac{\\sqrt{\\var{a}} \\cdot \\sqrt{\\var{v}}}{\\sqrt{\\var{a}}} \\\\[0.5em]
&= \\frac{\\sqrt{\\var{a}}}{\\sqrt{\\var{a}}} \\cdot \\sqrt{\\var{v}} \\\\[0.5em]
&= \\simplify{{sqrt(a)/sqrt(a)}} \\cdot \\sqrt{\\var{v}} \\\\[0.5em]
&= \\sqrt{\\var{v}} \\text{.}
\\end{align}
\\]
Oder
\n\\[
\\begin{align}
\\frac{\\sqrt{\\simplify{{a}*{v}}}}{\\sqrt{\\var{a}}} &= \\sqrt{\\frac{\\simplify{{a}*{v}}}{\\var{a}}} \\\\[0.5em]
&= \\sqrt{\\var{v}} \\text{.}
\\end{align}
\\]
Wir vereinfachen den Bruch folgendermaßen
\n\\[
\\begin{align}
\\frac{\\sqrt{\\simplify{({b}{m})^2*{s}}}}{\\var{m}} &= \\frac{\\sqrt{\\simplify{({b*m})^2}} \\cdot \\sqrt{\\var{s}}}{\\var{m}} \\\\[0.5em]
&= \\frac{\\simplify{{b*m}} \\cdot \\sqrt{\\var{s}}}{\\var{m}} \\\\[0.5em]
&= \\simplify{{b}*sqrt({s})} \\text{.}
\\end{align}
\\]
\\[
\\begin{align}
\\simplify{{d}sqrt({a}) - {b}sqrt({v}^2{a})+{n}sqrt({b}^2*{a})} &= \\var{d}\\sqrt{\\var{a}} - \\var{b}(\\sqrt{\\simplify{{v}^2}} \\cdot \\sqrt{\\var{a}})+\\var{n}(\\sqrt{\\simplify{{b}^2}} \\cdot \\sqrt{\\var{a}}) \\\\
&= \\var{d}\\sqrt{\\var{a}} -\\var{b}(\\simplify{{v}*sqrt({a})})+\\var{n}(\\simplify{{b}*sqrt({a})}) \\\\
&= \\simplify{{d}sqrt({a})}-\\simplify{{b}*{v}sqrt({a})}+\\simplify{{n}*{b}sqrt({a})} \\\\
&= \\simplify{({d}-{b}*{v}+{n}*{b})sqrt({a})} \\text{.}
\\end{align}
\\]
Wir schreiben $\\displaystyle\\frac{1}{\\sqrt{a}}$ als Bruch mit einer ganzen Zahl im Nenner, indem wir mit $\\sqrt{a}$ erweitern.
\n\\[
\\begin{align}
\\frac{1}{\\sqrt{\\var{a}}} &= \\frac{1}{\\sqrt{\\var{a}}} \\cdot \\frac{\\sqrt{\\var{a}}}{\\sqrt{\\var{a}}} \\\\[0.5em]
&= \\frac{\\sqrt{\\var{a}}}{\\var{a}} \\text{.}
\\end{align}
\\]
In diesem Fall erweitern wir mit $a-\\sqrt{b}$.
\n\\[
\\begin{align}
\\frac{1}{\\var{n}+\\sqrt{\\var{a}}} &= \\frac{1}{\\var{n}+\\sqrt{\\var{a}}} \\cdot \\frac{\\var{n}-\\sqrt{\\var{a}}}{\\var{n}-\\sqrt{\\var{a}}} \\\\[0.5em]
&=\\frac{\\var{n}-\\sqrt{\\var{a}}}{(\\var{n}+\\sqrt{\\var{a}})(\\var{n}-\\sqrt{\\var{a}})} \\\\[0.5em]
&=\\frac{\\var{n}-\\sqrt{\\var{a}}}{\\simplify{{n}^2}-\\var{a}} \\\\[0.5em]
&=\\frac{\\var{n}-\\sqrt{\\var{a}}}{\\simplify{{n}^2-{a}}} \\text{.}
\\end{align}
\\]
Wir erweitern mit $a+\\sqrt{b}$.
\n\\[
\\begin{align}
\\frac{\\var{t}}{\\var{d+p}-\\sqrt{\\var{p}}} &= \\frac{\\var{t}}{\\var{d+p}-\\sqrt{\\var{p}}} \\cdot \\frac{\\var{d+p}+\\sqrt{\\var{p}}}{\\var{d+p}+\\sqrt{\\var{p}}} \\\\[0.5em]
&=\\frac{\\var{t}(\\var{d+p}+\\sqrt{\\var{p}})}{(\\var{d+p}-\\sqrt{\\var{p}})(\\var{d+p}+\\sqrt{\\var{p}})} \\\\[0.5em]
&=\\frac{\\var{t}(\\var{d+p}+\\sqrt{\\var{p}})}{\\simplify{{d+p}^2}-\\var{p}} \\\\[0.5em]
&=\\frac{\\var{t}(\\var{d+p}+\\sqrt{\\var{p}})}{\\simplify{{d+p}^2-{p}}} \\\\[0.5em]
&=\\simplify{{t}/{(d+p)^2-p}}(\\var{d+p}+\\sqrt{\\var{p}}) \\\\[0.5em]
&= \\simplify[all,!noleadingMinus]{({t*(d+p)}+{t}*sqrt({p}))/({(d+p)^2-p})} \\text{.}
\\end{align}
\\]
all numbers from 3-10 for parts a, b, e, g
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\n$\\sqrt{\\simplify{{n}^2*{p}}} =$ [[0]]$\\sqrt{\\var{p}}$.
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\n$\\sqrt{(ab)} = \\sqrt{a} \\times \\sqrt{b}$.
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\n$\\displaystyle\\frac{\\sqrt{\\simplify{{a}*{v}}}}{\\sqrt{\\var{a}}} =$ [[0]].
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\n$\\sqrt{(ab)} = \\sqrt{a} \\times \\sqrt{b}$.
\n$\\displaystyle\\sqrt{\\frac{a}{b}} = \\displaystyle\\frac{\\sqrt{a}}{\\sqrt{b}}$.
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\n$\\displaystyle\\frac{\\sqrt{\\simplify{({b}*{m})^2*{s}}}}{\\var{m}} =$ [[0]]$\\sqrt{\\var{s}}$.
\n", "gaps": [{"type": "jme", "useCustomName": false, "customName": "", "marks": "2", "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "answer": "{b}", "answerSimplification": "all", "showPreview": true, "checkingType": "absdiff", "checkingAccuracy": 0.001, "failureRate": 1, "vsetRangePoints": 5, "vsetRange": [0, 1], "checkVariableNames": false, "singleLetterVariables": false, "allowUnknownFunctions": true, "implicitFunctionComposition": false, "valuegenerators": []}], "sortAnswers": false}, {"type": "gapfill", "useCustomName": false, "customName": "", "marks": 0, "scripts": {}, "customMarkingAlgorithm": "", "extendBaseMarkingAlgorithm": true, "unitTests": [], "showCorrectAnswer": true, "showFeedbackIcon": true, "variableReplacements": [], "variableReplacementStrategy": "originalfirst", "nextParts": [], "suggestGoingBack": false, "adaptiveMarkingPenalty": 0, "exploreObjective": null, "prompt": "Vereinfachen Sie $\\simplify{{d}sqrt({a}) - {b}sqrt({v}^2*{a})+{n}sqrt({b}^2*{a})}$.
\n$\\simplify{{d}sqrt({a}) - {b}sqrt({v}^2*{a})+{n}sqrt({b}^2*{a})} =$ [[0]].
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$\\displaystyle\\frac{1}{\\sqrt{\\var{a}}} =$
Um die Wurzel im Nenner von $\\frac{1}{\\sqrt{a}}$ \"loszuwerden\", erweitern Sie mit $\\sqrt{a}$.
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\n$\\displaystyle\\frac{1}{\\var{n}+\\sqrt{\\var{a}}} =$
In diesem Fall können Sie den Wurzelausdruck im Nenner von $\\displaystyle\\frac{1}{a+\\sqrt{b}}$ loswerden, indem Sie mit $a-\\sqrt{b}$ erweitern (und die dritte binomische Formel benutzen).
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\n$\\displaystyle\\frac{\\var{t}}{\\var{d+p}-\\sqrt{\\var{p}}} =$
Erweitern Sie mit ${a+\\sqrt{b}}$.
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