1.5: Exercises

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    From LibreTexts, under CC BY-NC-SA 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

    Exercise \(\PageIndex{1}\)

    Give examples of numbers that are

    1. natural numbers
    2. integers
    3. integers but not natural numbers
    4. rational numbers
    5. real numbers
    6. rational numbers but not integers
    Answer
    1. \(2, 3, 5\)
    2. \(−3, 0, 6\)
    3. \(−3, −4, 0\)
    4. \(\dfrac{2}{3}, \dfrac{-4}{7}, 8\)
    5. \(\sqrt{5}, \pi, \sqrt[3]{31}\)
    6. \(\dfrac{1}{2}, \dfrac{2}{5}, 0.75\)

    Exercise \(\PageIndex{2}\)

    Which of the following numbers are natural numbers, integers, rational numbers, or real numbers? Which of these numbers are irrational?

    1. \(\dfrac 7 3\)
    2. \(-5\)
    3. \(0\)
    4. \(17,000\)
    5. \(\dfrac{12}{4}\)
    6. \(\sqrt{7}\)
    7. \(\sqrt{25}\)
    Answer
    1. rational
    2. integer, rational
    3. integer, rational
    4. natural, integer, rational
    5. natural, integer, rational
    6. irrational
    7. natural, integer, rational

    All of the given numbers are real numbers

    Exercise \(\PageIndex{3}\)

    Evaluate the following absolute value expressions:

    1. \(|-8|\)
    2. \(|10|\)
    3. \(|-99|\)
    4. \(-|3|\)
    5. \(-|-2|\)
    6. \(|-\sqrt{6}|\)
    7. \(|3+4|\)
    8. \(|2-9|\)
    9. \(|-5.4|\)
    10. \(\left|-\dfrac{2}{3}\right|\)
    11. \(\left|\dfrac{5}{-2}\right|\)
    12. \(-\left|-\dfrac{-6}{-3}\right|\)
    Answer
    1. \(8\)
    2. \(10\)
    3. \(99\)
    4. \(-3\)
    5. \(-2\)
    6. \(\sqrt{6}\)
    7. \(7\)
    8. \(7\)
    9. \(5.4\)
    10. \(\dfrac{2}{3}\)
    11. \(\dfrac{5}{2}\)
    12. \(-2\)

    Exercise \(\PageIndex{4}\)

    Solve for \(x\):

    1. \(|x|=8\)
    2. \(|x|=0\)
    3. \(|x|=-3\)
    4. \(|x+3|=10\)
    5. \(|2x+5|=9\)
    6. \(|2-5x|=22\)
    7. \(|4x|=-8\)
    8. \(|-7x-3|=0\)
    9. \(|4-4x|=44\)
    10. \(-2\cdot |2-3x|=-12\)
    11. \(5+|2x+7|=14\)
    12. \(-|-8-2x|=-12\)
    Answer
    1. \(S=\{-8,8\}\)
    2. \(S=\{0\}\)
    3. \(S=\{\}\)
    4. \(S=\{-13,7\}\)
    5. \(S=\{-7,2\}\)
    6. \(S=\left\{-4, \dfrac{24}{5}\right\}\)
    7. \(S=\{\}\)
    8. \(S=\left\{\dfrac{-3}{7}\right\}\)
    9. \(S=\{-10,12\}\)
    10. \(S=\left\{\dfrac{-4}{3}, \dfrac{8}{3}\right\}\)
    11. \(S=\{-8,1\}\)
    12. \(S=\{-10,2\}\)

    Exercise \(\PageIndex{5}\)

    Solve for \(x\) using the geometric interpretation of the absolute value:

    1. \(|x|=8\)
    2. \(|x|=0\)
    3. \(|x|=-3\)
    4. \(|x-4|=2\)
    5. \(|x+5|=9\)
    6. \(|2-x|=5\)
    Answer
    1. \(S=\{-8,8\}\)
    2. \(S=\{0\}\)
    3. \(S=\{\}\)
    4. \(S=\{2,6\}\)
    5. \(S=\{-14,4\}\)
    6. \(S=\{-3,7\}\)

    Exercise \(\PageIndex{6}\)

    Complete the table.

    Inequality notation Number line Interval notation
    \(2\leq x< 5\)    
    \(x\leq 3\)    
      clipboard_ee36fbb8a1140f74a4f63d1e8e3ff679a.png  
      clipboard_e6c534d4d0379a6b2fddb24f85dc1f57e.png  
        \([-2,6]\)
        \((-\infty,0)\)
      clipboard_ee530401a798598d9e9a7c8efd7988e37.png  
    \(5< x\leq \sqrt{30}\)    
        \(\left(\dfrac{13}{7},\pi \right )\)
    Answer
    Inequality notation Number line Interval notation
    \(2\leq x< 5\) clipboard_ecc556141ef9c6812ed11f16885af51e9.png \([2,5)\)
    \(x\leq 3\) clipboard_e7d2ae6b9269b96fcb9abdf5ab7067ab5.png \((-\infty, 3]\)
    \(12<x \leq 17\) clipboard_ee36fbb8a1140f74a4f63d1e8e3ff679a.png \((12,17]\)
    \(x< -2\) clipboard_e6c534d4d0379a6b2fddb24f85dc1f57e.png \((-\infty,-2)\)
    \(-2 \leq x \leq 6\) clipboard_e98502b65d85cdc5539d27cf17265fc06.png \([-2,6]\)
    \(x< 0\) clipboard_ecc1e5c8860f45a8764dba047a1cdfcb3.png \((-\infty,0)\)
    \(4.5 \leq x\) clipboard_ee530401a798598d9e9a7c8efd7988e37.png \([4.5, \infty)\)
    \(5< x\leq \sqrt{30}\) clipboard_ea672b8a6eaaa02d6a68eec34566831e7.png \((5, \sqrt{30}]\)
    \(\dfrac{13}{7}<x<\pi\) clipboard_edc9edf9b56a08bf45919a6fc47142c9a.png \(\left(\dfrac{13}{7},\pi \right )\)

    Exercise \(\PageIndex{7}\)

    Solve for \(x\) and write the solution in interval notation.

    1. \(|x-4|\leq 7\)
    2. \(|x-4|\geq 7\)
    3. \(|x-4|> 7\)
    4. \(|2x+7|\leq 13\)
    5. \(|-2-4x|>8\)
    6. \(|4x+2|<17\)
    7. \(|15-3x|\geq 6\)
    8. \(\left|5x-\dfrac 4 3 \right|>\dfrac 2 3\)
    9. \(\left| \sqrt{2}x-\sqrt{2}\right|\leq \sqrt{8}\)
    10. \(|2x+3|<-5\)
    11. \(|5+5x|\geq -2\)
    12. \(|5+5x|> 0\)
    Answer
    1. \(S=[-3,11]\)
    2. \(S=(-\infty,-3] \cup[11, \infty)\)
    3. \(S=(-\infty,-3) \cup(11, \infty)\)
    4. \(S=[-10,3],\)
    5. \(S=\left(-\infty,-\dfrac{5}{2}\right) \cup\left(\dfrac{3}{2}, \infty\right)\)
    6. \(S=\left(\dfrac{-19}{4}, \dfrac{15}{4}\right)\)
    7. \(S=(-\infty, 3] \cup[7, \infty)\)
    8. \(S=\left(-\infty, \dfrac{2}{15}\right) \cup\left(\dfrac{2}{5}, \infty\right)\)
    9. \(S=[-1,3]\)
    10. \(S=\{\}\)
    11. \(S=(-\infty, \infty)=\mathbb{R}\)
    12. \(S=(-\infty,-1) \cup(-1, \infty)=\mathbb{R}-\{-1\}\)

    This page titled 1.5: Exercises was last modified on Mon, 02 May 2022 15:49:55 GMT and is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Thomas Tradler and Holly Carley (New York City College of Technology at CUNY Academic Works) via source content that was edited to the style and standards of the LibreTexts platform.