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For the following examples, tick the correct box to determine whether or not they are a surd.

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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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Surd

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Not a surd

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Match each surd with the equivalent simplification.

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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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Simplify the following surds:

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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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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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Surds are square roots that cannot be simplified to a whole number. They have a decimal equivalent but their decimal representations are never-ending. Therefore, it is often easier to leave surds as they are in algebraic calculations.

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(a)

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$\\sqrt{\\var{square}}$ and $\\sqrt[3]{\\var{cube}}$ are not surds, as they can be simplified to whole integers: $\\simplify{{sqrt(square)}}$ and $\\var{root}$ respectively. They are roots, but not surds. All surds are roots but not all roots are surds.

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$\\sqrt{\\var{h}}$, $\\sqrt{\\var{j}}$ and $\\sqrt{\\var{k}}$ are surds, as they cannot be simplified to a whole integer. There is no number, $b$, such that $b^2=\\var{h}, \\var{j}$ or $\\var{k}$. Therefore, $\\sqrt{\\var{h}}$, $\\sqrt{\\var{j}}$ and $\\sqrt{\\var{k}}$ are both roots and surds.

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(b)

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Suppose we want to simplify $\\sqrt x$. If we can find a square number $a^2$ which divides into $x$, we can write $x = a^2b$ where $b$ is an integer.

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Then we can simplify $\\sqrt x=\\sqrt {a^2b}=\\sqrt {a^2} \\times \\sqrt{b}=a \\sqrt {b}$

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i)

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$\\sqrt{48}=\\sqrt{16 \\times 3}$ = $\\sqrt{16}\\times\\sqrt3$

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$\\sqrt{16}$ simplifies down to $4$ so the final answer is: $4\\sqrt3$.

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ii)

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

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$\\sqrt4$ simplifies down to $2$ so the final answer is: $2\\sqrt{14}$.

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iii)

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

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$\\sqrt{16}$ simplifies down to $4$ so the final answer is: $4\\sqrt2$.

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iv)

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

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$\\sqrt4$ simplifies down to $2$ so the final answer is: $2\\sqrt{11}$.

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(c)

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This question requires you to notice that $\\var{a}$ and $\\var{d}$ are square numbers which are factors of $\\var{c}$ and $\\var{g}$ respectively. We can thus split each square root into a multiplication of two roots, and simplify as in part (b).

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

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and

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

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