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Grade 11 · Math · Algebra 2

11th grade Quadratic equations with complex solutions worksheet

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Quadratic equations with complex solutions

Grade 11 Math Worksheet - Challenge Me

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Circle the best answer, or write your answer on the line.

  1. Zee checks whether 2 − 5i solves x² − 4x + 29 = 0. What is (2 − 5i)² − 4(2 − 5i) + 29?

  2. Jun checks whether -1 + i solves x² + 2x + 5 = 0. What is (-1 + i)² + 2(-1 + i) + 5?

  3. Kira checks whether 3 − i solves x² − 6x + 10 = 0. What is (3 − i)² − 6(3 − i) + 10?

  4. Luz builds a puzzle whose solutions are 3 + 2i and 3 − 2i. Type x² as x^2. Which x² + bx + c has these solutions?

  5. Milo builds a puzzle whose solutions are -2 + 5i and -2 − 5i. Type x² as x^2. Which x² + bx + c has these solutions?

  6. Noah builds a puzzle whose solutions are 4 + i and 4 − i. Type x² as x^2. Which x² + bx + c has these solutions?

  7. Pia builds a puzzle whose solutions are -5 + 2i and -5 − 2i. Type x² as x^2. Which x² + bx + c has these solutions?

  8. Ren solves x² + 20 = 4x for a math club puzzle. Which shows both solutions?

    • x = 2 ± 2√6
    • x = -2 ± 4i
    • x = 2 ± 4i
    • x = 2 ± 8i
  9. Zee's robot solves x² + 34 = 6x. Which shows both solutions?

    • x = 3 ± 5i
    • x = 3 ± 10i
    • x = -3 ± 5i
    • x = 3 ± √43
  10. Esme solves x² + 13 = -4x on the board. Which shows both solutions?

    • x = -2 ± 6i
    • x = 2 ± 3i
    • x = -2 ± √17
    • x = -2 ± 3i
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11th grade Quadratic equations with complex solutions worksheet – printable
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About this worksheet

Quadratic equations with complex solutions. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

  • I can find b² − 4ac and say that a negative value gives two solutions with i.
  • I can solve a quadratic with the formula or square roots and write the solutions as a ± bi.
  • I can check a solution by substituting it, and build a quadratic from its two solutions.

Standard: N-CN.C.7, A-REI.B.4

Words to know

discriminant: b² − 4ac, the number under the root in the formula.

mirror pair: a + bi and a − bi: one above the real axis, one below.

± (plus or minus): Do it twice: once with +, once with −.

substitute: Put a number in for x and work it out.

Common mistakes

Your child added 4ac instead of subtracting it.

Your child doubled b instead of squaring it.

Your child made b² negative when b was negative.

What to say

Ask: in b² − 4ac, is 4ac added or taken away?

Ask: is b² the same as 2 × b?

Ask: what is (-6) × (-6)?

Questions parents ask

What is the most common mistake with quadratic equations with complex solutions?

Your child added 4ac instead of subtracting it.

How can I help my child with quadratic equations with complex solutions?

Ask: in b² − 4ac, is 4ac added or taken away?

Are these 11th grade math worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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