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Mathematics LibreTexts

9.3E: Exercises

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    Practice Makes Perfect

    In the following exercises, solve by using the Quadratic Formula.

    1. \(4 m^{2}+m-3=0\)

    2. \(4 n^{2}-9 n+5=0\)

    3. \(2 p^{2}-7 p+3=0\)

    4. \(3 q^{2}+8 q-3=0\)

    5. \(p^{2}+7 p+12=0\)

    6. \(q^{2}+3 q-18=0\)

    7. \(r^{2}-8 r=33\)

    8. \(t^{2}+13 t=-40\)

    9. \(3 u^{2}+7 u-2=0\)

    10. \(2 p^{2}+8 p+5=0\)

    11. \(2 a^{2}-6 a+3=0\)

    12. \(5 b^{2}+2 b-4=0\)

    13. \(x^{2}+8 x-4=0\)

    14. \(y^{2}+4 y-4=0\)

    15. \(3 y^{2}+5 y-2=0\)

    16. \(6 x^{2}+2 x-20=0\)

    17. \(2 x^{2}+3 x+3=0\)

    18. \(2 x^{2}-x+1=0\)

    19. \(8 x^{2}-6 x+2=0\)

    20. \(8 x^{2}-4 x+1=0\)

    21. \((v+1)(v-5)-4=0\)

    22. \((x+1)(x-3)=2\)

    23. \((y+4)(y-7)=18\)

    24. \((x+2)(x+6)=21\)

    25. \(\dfrac{1}{3} m^{2}+\dfrac{1}{12} m=\dfrac{1}{4}\)

    26. \(\dfrac{1}{3} n^{2}+n=-\dfrac{1}{2}\)

    27. \(\dfrac{3}{4} b^{2}+\dfrac{1}{2} b=\dfrac{3}{8}\)

    28. \(\dfrac{1}{9} c^{2}+\dfrac{2}{3} c=3\)

    29. \(16 c^{2}+24 c+9=0\)

    30. \(25 d^{2}-60 d+36=0\)

    31. \(25 q^{2}+30 q+9=0\)

    32. \(16 y^{2}+8 y+1=0\)

    Answer

    1. \(m=-1, m=\dfrac{3}{4}\)

    3. \(p=\dfrac{1}{3}, p=2\)

    5. \(p=-4, p=-3\)

    7. \(r=-3, r=11\)

    9. \(u=\dfrac{-7 \pm \sqrt{73}}{6}\)

    11. \(a=\dfrac{3 \pm \sqrt{3}}{2}\)

    13. \(x=-4 \pm 2 \sqrt{5}\)

    15. \(y=-\dfrac{2}{3}, y=-1\)

    17. \(x=-\dfrac{3}{4} \pm \dfrac{\sqrt{15}}{4} i\)

    19. \(x=\dfrac{3}{8} \pm \dfrac{\sqrt{7}}{8} i\)

    21. \(v=2 \pm 2 \sqrt{2}\)

    23. \(y=-4, y=7\)

    25. \(m=-1, m=\dfrac{3}{4}\)

    27. \(b=\dfrac{-2 \pm \sqrt{11}}{6}\)

    29. \(c=-\dfrac{3}{4}\)

    31. \(q=-\dfrac{3}{5}\)

    In the following exercises, determine the number of real solutions for each quadratic equation.

      1. \(4 x^{2}-5 x+16=0\)
      2. \(36 y^{2}+36 y+9=0\)
      3. \(6 m^{2}+3 m-5=0\)
      1. \(9 v^{2}-15 v+25=0\)
      2. \(100 w^{2}+60 w+9=0\)
      3. \(5 c^{2}+7 c-10=0\)
      1. \(r^{2}+12 r+36=0\)
      2. \(8 t^{2}-11 t+5=0\)
      3. \(3 v^{2}-5 v-1=0\)
      1. \(25 p^{2}+10 p+1=0\)
      2. \(7 q^{2}-3 q-6=0\)
      3. \(7 y^{2}+2 y+8=0\)
      5. Answer

      33. a. no real solutions b. \(1\) c. \(2\)

      35. a. \(1\) b. no real solutions c. \(2\)

    In the following exercises, identify the most appropriate method (Factoring, Square Root, or Quadratic Formula) to use to solve each quadratic equation. Do not solve.

      1. \(x^{2}-5 x-24=0\)
      2. \((y+5)^{2}=12\)
      3. \(14 m^{2}+3 m=11\)
      1. \((8 v+3)^{2}=81\)
      2. \(w^{2}-9 w-22=0\)
      3. \(4 n^{2}-10=6\)
      1. \(6 a^{2}+14=20\)
      2. \(\left(x-\dfrac{1}{4}\right)^{2}=\dfrac{5}{16}\)
      3. \(y^{2}-2 y=8\)
      1. \(8 b^{2}+15 b=4\)
      2. \(\dfrac{5}{9} v^{2}-\dfrac{2}{3} v=1\)
      3. \(\left(w+\dfrac{4}{3}\right)^{2}=\dfrac{2}{9}\)
      5. Answer

      37. a. Factor b. Square Root c. Quadratic Formula

      39. a. Quadratic Formula b. Square Root c. Factor

    1. Solve the equation \(x^{2}+10 x=120\)
      1. by completing the square
      2. using the Quadratic Formula
      3. Which method do you prefer? Why?
    2. Solve the equation \(12 y^{2}+23 y=24\)
      1. by completing the square
      2. using the Quadratic Formula
      3. Which method do you prefer? Why?
      3. Answer

      41. Answers will vary

    Self Check

    a. After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

    This table provides a checklist to evaluate mastery of the objectives of this section. Choose how would you respond to the statement “I can solve quadratic equations using the quadratic formula.” “Confidently,” “with some help,” or “No, I don’t get it.” Choose how would you respond to the statement “I can use the discriminant to predict the number of solutions of a quadratic equation.” “Confidently,” “with some help,” or “No, I don’t get it.” Choose how would you respond to the statement “I can identify the most appropriate method to use to solve a quadratic equation.” “Confidently,” “with some help,” or “No, I don’t get it.”
    Figure 9.3.87

    b. What does this checklist tell you about your mastery of this section? What steps will you take to improve?