9.4E: Exercises
- Page ID
- 30278
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\(\newcommand{\avec}{\mathbf a}\) \(\newcommand{\bvec}{\mathbf b}\) \(\newcommand{\cvec}{\mathbf c}\) \(\newcommand{\dvec}{\mathbf d}\) \(\newcommand{\dtil}{\widetilde{\mathbf d}}\) \(\newcommand{\evec}{\mathbf e}\) \(\newcommand{\fvec}{\mathbf f}\) \(\newcommand{\nvec}{\mathbf n}\) \(\newcommand{\pvec}{\mathbf p}\) \(\newcommand{\qvec}{\mathbf q}\) \(\newcommand{\svec}{\mathbf s}\) \(\newcommand{\tvec}{\mathbf t}\) \(\newcommand{\uvec}{\mathbf u}\) \(\newcommand{\vvec}{\mathbf v}\) \(\newcommand{\wvec}{\mathbf w}\) \(\newcommand{\xvec}{\mathbf x}\) \(\newcommand{\yvec}{\mathbf y}\) \(\newcommand{\zvec}{\mathbf z}\) \(\newcommand{\rvec}{\mathbf r}\) \(\newcommand{\mvec}{\mathbf m}\) \(\newcommand{\zerovec}{\mathbf 0}\) \(\newcommand{\onevec}{\mathbf 1}\) \(\newcommand{\real}{\mathbb R}\) \(\newcommand{\twovec}[2]{\left[\begin{array}{r}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\ctwovec}[2]{\left[\begin{array}{c}#1 \\ #2 \end{array}\right]}\) \(\newcommand{\threevec}[3]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\cthreevec}[3]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \end{array}\right]}\) \(\newcommand{\fourvec}[4]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\cfourvec}[4]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \end{array}\right]}\) \(\newcommand{\fivevec}[5]{\left[\begin{array}{r}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\cfivevec}[5]{\left[\begin{array}{c}#1 \\ #2 \\ #3 \\ #4 \\ #5 \\ \end{array}\right]}\) \(\newcommand{\mattwo}[4]{\left[\begin{array}{rr}#1 \amp #2 \\ #3 \amp #4 \\ \end{array}\right]}\) \(\newcommand{\laspan}[1]{\text{Span}\{#1\}}\) \(\newcommand{\bcal}{\cal B}\) \(\newcommand{\ccal}{\cal C}\) \(\newcommand{\scal}{\cal S}\) \(\newcommand{\wcal}{\cal W}\) \(\newcommand{\ecal}{\cal E}\) \(\newcommand{\coords}[2]{\left\{#1\right\}_{#2}}\) \(\newcommand{\gray}[1]{\color{gray}{#1}}\) \(\newcommand{\lgray}[1]{\color{lightgray}{#1}}\) \(\newcommand{\rank}{\operatorname{rank}}\) \(\newcommand{\row}{\text{Row}}\) \(\newcommand{\col}{\text{Col}}\) \(\renewcommand{\row}{\text{Row}}\) \(\newcommand{\nul}{\text{Nul}}\) \(\newcommand{\var}{\text{Var}}\) \(\newcommand{\corr}{\text{corr}}\) \(\newcommand{\len}[1]{\left|#1\right|}\) \(\newcommand{\bbar}{\overline{\bvec}}\) \(\newcommand{\bhat}{\widehat{\bvec}}\) \(\newcommand{\bperp}{\bvec^\perp}\) \(\newcommand{\xhat}{\widehat{\xvec}}\) \(\newcommand{\vhat}{\widehat{\vvec}}\) \(\newcommand{\uhat}{\widehat{\uvec}}\) \(\newcommand{\what}{\widehat{\wvec}}\) \(\newcommand{\Sighat}{\widehat{\Sigma}}\) \(\newcommand{\lt}{<}\) \(\newcommand{\gt}{>}\) \(\newcommand{\amp}{&}\) \(\definecolor{fillinmathshade}{gray}{0.9}\)Practice Makes Perfect
Multiply Square Roots
In the following exercises, simplify.
- \(\sqrt{2}·\sqrt{8}\)
- \((3\sqrt{3})(2\sqrt{18})\)
- Answer
-
- \(44\)
- \(18\sqrt{6}\)
- \(\sqrt{6}·\sqrt{6}\)
- \((3\sqrt{2})(2\sqrt{32})\)
- \(\sqrt{7}·\sqrt{14}\)
- \((4\sqrt{8})(5\sqrt{8})\)
- Answer
-
- \(7\sqrt{2}\)
- 160
- \(\sqrt{6}·\sqrt{12}\)
- \((2\sqrt{5})(2\sqrt{10})\)
\((5\sqrt{2})(3\sqrt{6})\)
- Answer
-
\(30\sqrt{3}\)
\((2\sqrt{3})(4\sqrt{6})\)
\((−2\sqrt{3})(3\sqrt{18})\)
- Answer
-
\(−18\sqrt{6}\)
\((−4\sqrt{5})(5\sqrt{10})\)
\((5\sqrt{6})(−\sqrt{12})\)
- Answer
-
\(−30\sqrt{2}\)
\((6\sqrt{2})(−\sqrt{10})\)
\((−2\sqrt{7})(−2\sqrt{14})\)
- Answer
-
\(28\sqrt{2}\)
\((−2\sqrt{11})(−4\sqrt{22})\)
- \((\sqrt{15y})(\sqrt{5y^3})\)
- \((\sqrt{2n^2})(\sqrt{18n^3})\)
- Answer
-
- \(5y^2\sqrt{3}\)
- \(6n^2\sqrt{n}\)
- \((\sqrt{14x^3})(\sqrt{7x^3})\)
- \((\sqrt{3q^2})(\sqrt{48q^3})\)
- \((\sqrt{16y^2})(\sqrt{8y^4})\)
- \((\sqrt{11s^6})(\sqrt{11s})\)
- Answer
-
- \(8y^3\sqrt{2}\)
- \(11s^3\sqrt{s}\)
ⓐ \((\sqrt{8x^3})(\sqrt{3x})\)
ⓑ \((\sqrt{7r})(\sqrt{7r^8})\)
\((2\sqrt{5b^3})(4\sqrt{15b})\)
- Answer
-
\(40b^2\sqrt{3}\)
\((\sqrt{38c^5})(\sqrt{26c^3})\)
\((6\sqrt{3d^3})(4\sqrt{12d^5})\)
- Answer
-
\(144d^4\)
\((2\sqrt{5b^3})(4\sqrt{15b})\)
\((2\sqrt{5d^6})(3\sqrt{20d^2})\)
- Answer
-
\(60d^4\)
\((−2\sqrt{7z^3})(3\sqrt{14z^8})\)
\((4\sqrt{2k^5})(−3\sqrt{32k^6})\)
- Answer
-
\(−96k^5\sqrt{k}\)
- \((\sqrt{7})^2\)
- \((−\sqrt{15})^2\)
- \((\sqrt{11})^2\)
- \((−\sqrt{21})^2\)
- Answer
-
- 11
- 21
- \((\sqrt{19})^2\)
- \((−\sqrt{5})^2\)
- \((\sqrt{23})^2\)
- \((−\sqrt{3})^2\)
- Answer
-
- 23
- 3
- \((4\sqrt{11})(−3\sqrt{11})\)
- \((5\sqrt{3})^2\)
- \((2\sqrt{13})(−9\sqrt{13})\)
- \((6\sqrt{5})^2\)
- Answer
-
- −234
- 180
- \((−3\sqrt{12})(−2\sqrt{6})\)
- \( (−4\sqrt{10})^2\)
- \((−7\sqrt{5})(−3\sqrt{10})\)
- \( (−2\sqrt{14})^2\)
- Answer
-
- \(105\sqrt{2}\)
- 56
Use Polynomial Multiplication to Multiply Square Roots
In the following exercises, simplify.
- \(3(4−\sqrt{3})\)
- \(\sqrt{2}(4−\sqrt{6})\)
- \(4(6−\sqrt{11})\)
- \(\sqrt{2}(5−\sqrt{12})\)
- Answer
-
- \(24−4\sqrt{11}\)
- \(5\sqrt{2}−2\sqrt{6}\)
- \(5(3−\sqrt{7})\)
- \(\sqrt{3}(4−\sqrt{15})\)
- \(7(−2−\sqrt{11})\)
- \(\sqrt{7}(6−\sqrt{14})\)
- Answer
-
- \(−14−7\sqrt{11}\)
- \(6\sqrt{7}−7\sqrt{2}\)
- \(\sqrt{7}(5+2\sqrt{7})\)
- \(\sqrt{5}(\sqrt{10}+\sqrt{18})\)
- \(\sqrt{11}(8+4\sqrt{11})\)
- \(\sqrt{3}(\sqrt{12}+\sqrt{27})\)
- Answer
-
- \(44+8\sqrt{11}\)
- 15
- \(\sqrt{11}(−3+4\sqrt{1})\)
- \(\sqrt{3}(\sqrt{15}−\sqrt{18})\)
- \(\sqrt{2}(−5+9\sqrt{2})\)
- \(\sqrt{7}(\sqrt{3}−\sqrt{21})\)
- Answer
-
- \(18−5\sqrt{2}\)
- \(\sqrt{21}−7\sqrt{3}\)
\((8+\sqrt{3})(2−\sqrt{3})\)
\((7+\sqrt{3})(9−\sqrt{3})\)
- Answer
-
\(60+2\sqrt{3}\)
\((8−\sqrt{2})(3+\sqrt{2})\)
\((9−\sqrt{2})(6+\sqrt{2})\)
- Answer
-
\(52+3\sqrt{2}\)
\((3−\sqrt{7})(5−\sqrt{7})\)
\((5−\sqrt{7})(4−\sqrt{7})\)
- Answer
-
\(27−9\sqrt{7}\)
\((1+3\sqrt{10})(5−2\sqrt{10})\)
\((7−2\sqrt{5})(4+9\sqrt{5})\)
- Answer
-
\(−62+55\sqrt{5}\)
\((\sqrt{3}+\sqrt{10})(\sqrt{3}+2\sqrt{10})\)
\((\sqrt{11}+\sqrt{5})(\sqrt{11}+6\sqrt{5})\)
- Answer
-
\(41+7\sqrt{55}\)
\((2\sqrt{7}−5\sqrt{11})(4\sqrt{7}+9\sqrt{11})\)
\((4\sqrt{6}+7\sqrt{13})(8\sqrt{6}−3\sqrt{13})\)
- Answer
-
\(−81+44\sqrt{78}\)
\((5−\sqrt{u})(3+\sqrt{u})\)
\((9−\sqrt{w})(2+\sqrt{w})\)
- Answer
-
\(18+7\sqrt{w}\)
\((7+2\sqrt{m})(4+9\sqrt{m})\)
\((6+5\sqrt{n})(11+3\sqrt{n})\)
- Answer
-
\(66+73\sqrt{n}+15n\)
- \((3+\sqrt{5})^2\)
- \((2−5\sqrt{3})^2\)
- \((4+\sqrt{11})^2\)
- \((3−2\sqrt{5})^2\)
- Answer
-
- \(27+8\sqrt{11}\)
- \(29−12\sqrt{5}\)
- \((9−\sqrt{6})^2\)
- \((10+3\sqrt{7})^2\)
- \((5−\sqrt{10})^2\)
- \((8+3\sqrt{2})^2\)
- Answer
-
- \(35−10\sqrt{10}\)
- \(82+48\sqrt{2}\)
\((3−\sqrt{5})(3+\sqrt{5})\)
\((10−\sqrt{3})(10+\sqrt{3})\)
- Answer
-
97
\((4+\sqrt{2})(4−\sqrt{2})\)
\((7+\sqrt{10})(7−\sqrt{10})\)
- Answer
-
39
\((4+9\sqrt{3})(4−9\sqrt{3})\)
\((1+8\sqrt{2})(1−8\sqrt{2})\)
- Answer
-
−127
\((12−5\sqrt{5})(12+5\sqrt{5})\)
\((9−4\sqrt{3})(9+4\sqrt{3})\)
- Answer
-
33
Mixed Practice
In the following exercises, simplify.
\(\sqrt{3}·\sqrt{21}\)
\((4\sqrt{6})(−\sqrt{18})\)
- Answer
-
\(−24\sqrt{3}\)
\((−5+\sqrt{7})(6+\sqrt{21})\)
\((−5\sqrt{7})(6\sqrt{21})\)
- Answer
-
\(−210\sqrt{3}\)
\((−4\sqrt{2})(2\sqrt{18})\)
\((\sqrt{35y^3})(\sqrt{7y^3})\)
- Answer
-
\(7y^3\sqrt{5}\)
\((4\sqrt{12x^5})(2\sqrt{6x^3})\)
\((\sqrt{29})^2\)
- Answer
-
29
\((−4\sqrt{17})(−3\sqrt{17})\)
\((−4+\sqrt{17})(−3+\sqrt{17})\)
- Answer
-
\(29−7\sqrt{17}\)
Everyday Math
A landscaper wants to put a square reflecting pool next to a triangular deck, as shown below. The triangular deck is a right triangle, with legs of length 9 feet and 11 feet, and the pool will be adjacent to the hypotenuse.
- Use the Pythagorean Theorem to find the length of a side of the pool. Round your answer to the nearest tenth of a foot.
- Find the exact area of the pool.
An artist wants to make a small monument in the shape of a square base topped by a right triangle, as shown below. The square base will be adjacent to one leg of the triangle. The other leg of the triangle will measure 2 feet and the hypotenuse will be 5 feet.
- Use the Pythagorean Theorem to find the length of a side of the square base. Round your answer to the nearest tenth of a foot.
- Find the exact area of the face of the square base.
- Answer
-
- 4.6feet
- 21 sq. feet
A square garden will be made with a stone border on one edge. If only \(3+\sqrt{10}\) feet of stone are available, simplify \((3+\sqrt{10})^2\) to determine the area of the largest such garden.
A garden will be made so as to contain two square sections, one section with side length \(\sqrt{5}+\sqrt{6}\) yards and one section with side length \(\sqrt{2}+\sqrt{3}\) yards. Simplify \((\sqrt{5}+\sqrt{6})(\sqrt{2}+\sqrt{3})\) to determine the total area of the garden.
Suppose a third section will be added to the garden in the previous exercise. The third section is to have a width of \(\sqrt{432}\) feet. Write an expression that gives the total area of the garden.
Writing Exercises
- Explain why \((−\sqrt{n})^2\) is always positive, for \(n \ge 0\).
- Explain why \(−(\sqrt{n})^2\) is always negative, for \(n \ge 0\).
- Answer
-
- when squaring a negative, it becomes a positive
- since the negative is not included in the parenthesis, it is not squared, and remains negative
Use the binomial square pattern to simplify \((3+\sqrt{2})^2\). Explain all your steps.
Self Check
ⓐ After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.
ⓑ On a scale of 1–10, how would you rate your mastery of this section in light of your responses on the checklist? How can you improve this?