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This question tests the student's understanding of what is and is not a surd, and on their simplification of surds.

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Translated to German, minor changes to advice section.

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Original: https://numbas.mathcentre.ac.uk/question/22497/surds-simplification/ by Lauren Richards.

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Einige einfache Aufgaben zur Vereinfachung von Ausdrücken mit Quadratzahlen.

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a)

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$\\sqrt{\\var{square}}$ und $\\sqrt[3]{\\var{cube}}$ sind rational, und zwar sogar ganze Zahlen: $\\simplify{{sqrt(square)}}$ bzw. $\\var{root}$.

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$\\sqrt{\\var{h}}$, $\\sqrt{\\var{j}}$ und $\\sqrt{\\var{k}}$ sind irrational. Es gibt keine ganzen Zahlen $a, b$, $b\\ne 0$ so dass $\\left(\\frac ab\\right)^2=\\var{h}$ (oder $= \\var{j}$ oder $=\\var{k}$). Eine Möglichkeit, das zu sehen, ist, den Satz über die eindeutige Primzaktorzerlegung von ganzen Zahlen zu benutzen. Wenn $\\left(\\frac ab\\right)^2=\\var{h}$ gilt, also $a^2 = hb^2$, dann kommt in der eindeutigen Primfaktorzerlegung der linken Seite jede Primzahl mit einem geraden Exponenten vor; auf der rechten Seite ist das nicht der Fall.

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b)

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Benutzen SIe, dass $\\sqrt{a}\\times\\sqrt{b}=\\sqrt{ab}$.

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Wir suchen nach einer Quadratzahl, die $ab$ teilt, und schreiben das als $\\sqrt{b^2}\\times\\sqrt{a}$.

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i)

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$\\sqrt{48}$ = $\\sqrt{16}\\times\\sqrt3$

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$\\sqrt{16}$ ist $4$, also ist die Antwort: $4\\sqrt3$.

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ii)

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$\\sqrt{56}$ = $\\sqrt{4}\\times\\sqrt{14}$

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$\\sqrt4$ ist $2$, also erhalten wir: $2\\sqrt{14}$.

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iii)

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$\\sqrt{32}$ = $\\sqrt{16}\\times\\sqrt{2}$

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$\\sqrt{16}$ ist $4$, wir bekommen also: $4\\sqrt2$.

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iv)

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$\\sqrt{44}$ = $\\sqrt{4}\\times\\sqrt{11}$

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$\\sqrt4$ ist $2$, also erhalten wir: $2\\sqrt{11}$.

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c)

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Beachten Sie, dass $\\sqrt{\\var{a}}$ und $\\sqrt{\\var{d}}$ Wurzeln aus Quadratzahlen sind.

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$\\sqrt{\\var{a}}$ = $\\var{sqrta}$, folglich:

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i) $\\sqrt{\\var{c}}$ = $\\sqrt{\\var{a}}$ x $\\sqrt{\\var{b}}$ = $\\var{sqrta}\\sqrt{\\var{b}}$ and

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ii) $\\sqrt{\\var{g}}$ = $\\sqrt{\\var{d}}$ x $\\sqrt{\\var{f}}$ = $\\var{sqrtd}\\sqrt{\\var{f}}$.

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a times b

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square root of the squared numbers

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Random number between 1 and 12 except 4 and 9.

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Random squared number

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Welche der folgenden Zahlen sind rational (lassen sich als Bruchzahl darstellen), welche irrational (lassen sich nicht als Bruchzahl darstellen)?

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$\\sqrt{\\var{square}}$

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$\\sqrt{\\var{h}}$

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$^3\\sqrt{\\var{cube}}$

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$\\sqrt{\\var{j}}$

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$\\sqrt{\\var{k}}$

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Irrational

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Rational

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Vereinfachen Sie die Quadratwurzeln, indem Sie eine möglichst große Quadratzahl \"aus der Wurzel herausziehen\".

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[[0]]

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i) $\\sqrt{48}$

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ii) $\\sqrt{32}$

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iii) $\\sqrt{56}$

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iv) $\\sqrt{44}$

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$4\\sqrt3$

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$2\\sqrt{11}$

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$2\\sqrt{14}$

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$4\\sqrt{2}$

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Vereinfachen Sie:

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$\\displaystyle\\sqrt{\\var{c}}$ = [[0]]$\\displaystyle\\sqrt{\\var{b}}$

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$\\displaystyle\\sqrt{\\var{g}}$ = [[1]]$\\displaystyle\\sqrt{\\var{f}}$

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