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Students solve quadratic equations using the completing the square method and color the answers according to the provided color key.

Worksheet titled "Solving Quadratic Equations: Completing the Square Color by Number" with ten quadratic equations to solve by completing the square, each with a corresponding color for the answer.

Worksheet titled "Solving Quadratic Equations: Completing the Square Color by Number" with ten quadratic equations to solve by completing the square, each with a corresponding color for the answer.

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Show Answer Key & Explanations Step-by-step solution for: Solve Quadratic Equations by Completing the Square
To solve the quadratic equations by completing the square, we will follow these steps for each equation:

1. Rewrite the equation in standard form: Ensure the equation is in the form \( ax^2 + bx + c = 0 \).
2. Move the constant term to the other side: Isolate the \( x \)-terms on one side.
3. Complete the square: Add and subtract the square of half the coefficient of \( x \) inside the equation.
4. Solve for \( x \): Use the square root property to find the roots.

Let's solve each equation step by step.

---

Equation 1: \( x^2 + 8x - 14 = 6 \)



1. Rewrite the equation:
\[
x^2 + 8x - 14 - 6 = 0 \implies x^2 + 8x - 20 = 0
\]

2. Move the constant term:
\[
x^2 + 8x = 20
\]

3. Complete the square:
- Half of the coefficient of \( x \) is \( \frac{8}{2} = 4 \).
- Square it: \( 4^2 = 16 \).
- Add and subtract 16:
\[
x^2 + 8x + 16 - 16 = 20 \implies (x + 4)^2 - 16 = 20
\]
- Simplify:
\[
(x + 4)^2 = 36
\]

4. Solve for \( x \):
\[
x + 4 = \pm \sqrt{36} \implies x + 4 = \pm 6
\]
- \( x + 4 = 6 \implies x = 2 \)
- \( x + 4 = -6 \implies x = -10 \)

Roots: \( x = 2 \) and \( x = -10 \)

---

Equation 2: \( x^2 + 5x = -4 \)



1. Move the constant term:
\[
x^2 + 5x + 4 = 0
\]

2. Complete the square:
- Half of the coefficient of \( x \) is \( \frac{5}{2} \).
- Square it: \( \left( \frac{5}{2} \right)^2 = \frac{25}{4} \).
- Add and subtract \( \frac{25}{4} \):
\[
x^2 + 5x + \frac{25}{4} - \frac{25}{4} = -4 \implies \left( x + \frac{5}{2} \right)^2 - \frac{25}{4} = -4
\]
- Simplify:
\[
\left( x + \frac{5}{2} \right)^2 = \frac{25}{4} - \frac{16}{4} = \frac{9}{4}
\]

3. Solve for \( x \):
\[
x + \frac{5}{2} = \pm \sqrt{\frac{9}{4}} \implies x + \frac{5}{2} = \pm \frac{3}{2}
\]
- \( x + \frac{5}{2} = \frac{3}{2} \implies x = \frac{3}{2} - \frac{5}{2} = -1 \)
- \( x + \frac{5}{2} = -\frac{3}{2} \implies x = -\frac{3}{2} - \frac{5}{2} = -4 \)

Roots: \( x = -1 \) and \( x = -4 \)

---

Equation 3: \( x^2 + 7x + 10 = 0 \)



1. Move the constant term:
\[
x^2 + 7x = -10
\]

2. Complete the square:
- Half of the coefficient of \( x \) is \( \frac{7}{2} \).
- Square it: \( \left( \frac{7}{2} \right)^2 = \frac{49}{4} \).
- Add and subtract \( \frac{49}{4} \):
\[
x^2 + 7x + \frac{49}{4} - \frac{49}{4} = -10 \implies \left( x + \frac{7}{2} \right)^2 - \frac{49}{4} = -10
\]
- Simplify:
\[
\left( x + \frac{7}{2} \right)^2 = \frac{49}{4} - \frac{40}{4} = \frac{9}{4}
\]

3. Solve for \( x \):
\[
x + \frac{7}{2} = \pm \sqrt{\frac{9}{4}} \implies x + \frac{7}{2} = \pm \frac{3}{2}
\]
- \( x + \frac{7}{2} = \frac{3}{2} \implies x = \frac{3}{2} - \frac{7}{2} = -2 \)
- \( x + \frac{7}{2} = -\frac{3}{2} \implies x = -\frac{3}{2} - \frac{7}{2} = -5 \)

Roots: \( x = -2 \) and \( x = -5 \)

---

Equation 4: \( x^2 + 12x + 16 = -19 \)



1. Move the constant term:
\[
x^2 + 12x + 16 + 19 = 0 \implies x^2 + 12x + 35 = 0
\]

2. Complete the square:
- Half of the coefficient of \( x \) is \( \frac{12}{2} = 6 \).
- Square it: \( 6^2 = 36 \).
- Add and subtract 36:
\[
x^2 + 12x + 36 - 36 + 35 = 0 \implies (x + 6)^2 - 1 = 0
\]
- Simplify:
\[
(x + 6)^2 = 1
\]

3. Solve for \( x \):
\[
x + 6 = \pm \sqrt{1} \implies x + 6 = \pm 1
\]
- \( x + 6 = 1 \implies x = -5 \)
- \( x + 6 = -1 \implies x = -7 \)

Roots: \( x = -5 \) and \( x = -7 \)

---

Equation 5: \( x^2 - 4x - 91 = 7 \)



1. Rewrite the equation:
\[
x^2 - 4x - 91 - 7 = 0 \implies x^2 - 4x - 98 = 0
\]

2. Move the constant term:
\[
x^2 - 4x = 98
\]

3. Complete the square:
- Half of the coefficient of \( x \) is \( \frac{-4}{2} = -2 \).
- Square it: \( (-2)^2 = 4 \).
- Add and subtract 4:
\[
x^2 - 4x + 4 - 4 = 98 \implies (x - 2)^2 - 4 = 98
\]
- Simplify:
\[
(x - 2)^2 = 102
\]

4. Solve for \( x \):
\[
x - 2 = \pm \sqrt{102}
\]
- \( x - 2 = \sqrt{102} \implies x = 2 + \sqrt{102} \)
- \( x - 2 = -\sqrt{102} \implies x = 2 - \sqrt{102} \)

Roots: \( x = 2 + \sqrt{102} \) and \( x = 2 - \sqrt{102} \)

---

Equation 6: \( x^2 - 4x + 1 = -5 \)



1. Rewrite the equation:
\[
x^2 - 4x + 1 + 5 = 0 \implies x^2 - 4x + 6 = 0
\]

2. Move the constant term:
\[
x^2 - 4x = -6
\]

3. Complete the square:
- Half of the coefficient of \( x \) is \( \frac{-4}{2} = -2 \).
- Square it: \( (-2)^2 = 4 \).
- Add and subtract 4:
\[
x^2 - 4x + 4 - 4 = -6 \implies (x - 2)^2 - 4 = -6
\]
- Simplify:
\[
(x - 2)^2 = -2
\]

4. Solve for \( x \):
\[
x - 2 = \pm \sqrt{-2} \implies x - 2 = \pm i\sqrt{2}
\]
- \( x - 2 = i\sqrt{2} \implies x = 2 + i\sqrt{2} \)
- \( x - 2 = -i\sqrt{2} \implies x = 2 - i\sqrt{2} \)

Roots: \( x = 2 + i\sqrt{2} \) and \( x = 2 - i\sqrt{2} \)

---

Equation 7: \( x^2 + 12x = -32 \)



1. Move the constant term:
\[
x^2 + 12x + 32 = 0
\]

2. Complete the square:
- Half of the coefficient of \( x \) is \( \frac{12}{2} = 6 \).
- Square it: \( 6^2 = 36 \).
- Add and subtract 36:
\[
x^2 + 12x + 36 - 36 + 32 = 0 \implies (x + 6)^2 - 4 = 0
\]
- Simplify:
\[
(x + 6)^2 = 4
\]

3. Solve for \( x \):
\[
x + 6 = \pm \sqrt{4} \implies x + 6 = \pm 2
\]
- \( x + 6 = 2 \implies x = -4 \)
- \( x + 6 = -2 \implies x = -8 \)

Roots: \( x = -4 \) and \( x = -8 \)

---

Equation 8: \( 10x^2 - 45x - 12 = 43 \)



1. Rewrite the equation:
\[
10x^2 - 45x - 12 - 43 = 0 \implies 10x^2 - 45x - 55 = 0
\]

2. Divide by 5 to simplify:
\[
2x^2 - 9x - 11 = 0
\]

3. Move the constant term:
\[
2x^2 - 9x = 11
\]

4. Complete the square:
- Factor out 2 from the \( x \)-terms:
\[
2\left( x^2 - \frac{9}{2}x \right) = 11
\]
- Half of the coefficient of \( x \) is \( \frac{-9/2}{2} = -\frac{9}{4} \).
- Square it: \( \left( -\frac{9}{4} \right)^2 = \frac{81}{16} \).
- Add and subtract \( \frac{81}{16} \) inside the parentheses:
\[
2\left( x^2 - \frac{9}{2}x + \frac{81}{16} - \frac{81}{16} \right) = 11 \implies 2\left( \left( x - \frac{9}{4} \right)^2 - \frac{81}{16} \right) = 11
\]
- Distribute the 2:
\[
2\left( x - \frac{9}{4} \right)^2 - \frac{162}{16} = 11 \implies 2\left( x - \frac{9}{4} \right)^2 - \frac{81}{8} = 11
\]
- Simplify:
\[
2\left( x - \frac{9}{4} \right)^2 = 11 + \frac{81}{8} = \frac{88}{8} + \frac{81}{8} = \frac{169}{8}
\]
- Divide by 2:
\[
\left( x - \frac{9}{4} \right)^2 = \frac{169}{16}
\]

5. Solve for \( x \):
\[
x - \frac{9}{4} = \pm \sqrt{\frac{169}{16}} \implies x - \frac{9}{4} = \pm \frac{13}{4}
\]
- \( x - \frac{9}{4} = \frac{13}{4} \implies x = \frac{22}{4} = \frac{11}{2} \)
- \( x - \frac{9}{4} = -\frac{13}{4} \implies x = -\frac{4}{4} = -1 \)

Roots: \( x = \frac{11}{2} \) and \( x = -1 \)

---

Equation 9: \( x^2 = 12 - 4x \)



1. Rewrite the equation:
\[
x^2 + 4x - 12 = 0
\]

2. Move the constant term:
\[
x^2 + 4x = 12
\]

3. Complete the square:
- Half of the coefficient of \( x \) is \( \frac{4}{2} = 2 \).
- Square it: \( 2^2 = 4 \).
- Add and subtract 4:
\[
x^2 + 4x + 4 - 4 = 12 \implies (x + 2)^2 - 4 = 12
\]
- Simplify:
\[
(x + 2)^2 = 16
\]

4. Solve for \( x \):
\[
x + 2 = \pm \sqrt{16} \implies x + 2 = \pm 4
\]
- \( x + 2 = 4 \implies x = 2 \)
- \( x + 2 = -4 \implies x = -6 \)

Roots: \( x = 2 \) and \( x = -6 \)

---

Equation 10: \( 3x^2 = -4 + 8x \)



1. Rewrite the equation:
\[
3x^2 - 8x + 4 = 0
\]

2. Divide by 3 to simplify:
\[
x^2 - \frac{8}{3}x + \frac{4}{3} = 0
\]

3. Move the constant term:
\[
x^2 - \frac{8}{3}x = -\frac{4}{3}
\]

4. Complete the square:
- Half of the coefficient of \( x \) is \( \frac{-8/3}{2} = -\frac{4}{3} \).
- Square it: \( \left( -\frac{4}{3} \right)^2 = \frac{16}{9} \).
- Add and subtract \( \frac{16}{9} \):
\[
x^2 - \frac{8}{3}x + \frac{16}{9} - \frac{16}{9} = -\frac{4}{3} \implies \left( x - \frac{4}{3} \right)^2 - \frac{16}{9} = -\frac{4}{3}
\]
- Simplify:
\[
\left( x - \frac{4}{3} \right)^2 = \frac{16}{9} - \frac{12}{9} = \frac{4}{9}
\]

5. Solve for \( x \):
\[
x - \frac{4}{3} = \pm \sqrt{\frac{4}{9}} \implies x - \frac{4}{3} = \pm \frac{2}{3}
\]
- \( x - \frac{4}{3} = \frac{2}{3} \implies x = \frac{6}{3} = 2 \)
- \( x - \frac{4}{3} = -\frac{2}{3} \implies x = \frac{2}{3} \)

Roots: \( x = 2 \) and \( x = \frac{2}{3} \)

---

Final Answers



\[
\boxed{
\begin{array}{ccc}
\text{Equation} & \text{Roots} & \text{Color} \\
1. & x = 2, x = -10 & \text{Orange} \\
2. & x = -1, x = -4 & \text{Green} \\
3. & x = -2, x = -5 & \text{Purple} \\
4. & x = -5, x = -7 & \text{Blue} \\
5. & x = 2 + \sqrt{102}, x = 2 - \sqrt{102} & \text{Purple} \\
6. & x = 2 + i\sqrt{2}, x = 2 - i\sqrt{2} & \text{Teal} \\
7. & x = -4, x = -8 & \text{Pink} \\
8. & x = \frac{11}{2}, x = -1 & \text{Orange} \\
9. & x = 2, x = -6 & \text{Blue} \\
10. & x = 2, x = \frac{2}{3} & \text{Green} \\
\end{array}
}
\]
Parent Tip: Review the logic above to help your child master the concept of solving quadratic equations by completing the square worksheets.
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