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Lesson 13.4: Applications and Extensions — Practice Questions

  1. 1. The roots of the equation $4x^2 + 9x + 2 = 0$ are $-2$ and $-\frac{1}{4}$. Based on the root scaling property, what is the smaller root of the related equation $x^2 + 9x + 8 = 0$? ___

  2. 2. Let $r_1$ and $r_2$ be the roots of $5x^2 - 11x + 2 = 0$. Let $s_1$ and $s_2$ be the roots of $x^2 - 11x + 10 = 0$. What is the relationship between the roots?

    • A. The roots of the second equation are 5 times the roots of the first.
    • B. The roots of the first equation are 5 times the roots of the second.
    • C. The roots of the two equations are the same.
    • D. The roots of the second equation are the reciprocals of the roots of the first.
  3. 3. The roots of $x^2 - 8x + 12 = 0$ are $2$ and $6$. For the related equation $2x^2 - 8x + 6 = 0$, what is the larger root? ___

  4. 4. If the roots of the quadratic equation $3x^2 + 10x - 8 = 0$ are $r_1$ and $r_2$, which of the following equations has the roots $3r_1$ and $3r_2$?

    • A. $x^2 + 10x - 24 = 0$
    • B. $x^2 + 10x - 8 = 0$
    • C. $3x^2 + 10x - 24 = 0$
    • D. $x^2 + 30x - 72 = 0$
  5. 5. The roots of $x^2 - 5x - 6 = 0$ are $6$ and $-1$. The related equation $ax^2 - 5x + c = 0$ has roots that are $\frac{1}{2}$ times the roots of the first equation. What is the value of $c$? ___

  6. 6. What is the absolute difference between the roots of the quadratic equation $x^2 - 7x + 10 = 0$? ___

  7. 7. What is the absolute difference between the roots of the quadratic equation $3x^2 + 5x - 1 = 0$? ___

  8. 8. What is the absolute difference between the roots of the equation $-2x^2 + 6x - 1 = 0$?

    • A. $\sqrt{11}$
    • B. $\sqrt{7}$
    • C. $\frac{\sqrt{7}}{2}$
    • D. $2\sqrt{7}$
  9. 9. For which of the following quadratic equations is the absolute difference between the roots equal to 0?

    • A. $x^2 - 6x + 9 = 0$
    • B. $x^2 - 9 = 0$
    • C. $x^2 + 2x + 2 = 0$
    • D. $x^2 - 5x = 0$
  10. 10. Calculate the absolute difference between the roots of the equation $4x^2 - 25 = 0$. ___