Grade 11 · Math · Algebra 2

11th grade Add, subtract and multiply complex numbers worksheet

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Add, subtract and multiply complex numbers

Grade 11 Math Worksheet

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

Noah's robot multiplies two points on the complex plane. What is (2 + 3i)(4 − i)?
Pia multiplies on a math club card. What is (1 − 2i)(3 + 5i)?
Ren works out a product on the board. What is (-3 + i)(2 + 4i)?
Tala multiplies two pins on a grid map. What is (5 + 2i)(1 + 3i)?
Zee squares 3 + 2i to find where a kite sticker lands. What is (3 + 2i)²?
Jun's robot squares its spot, 1 + 5i. What is (1 + 5i)²?
Kira squares -2 + 3i on the class board. What is (-2 + 3i)²?
Luz multiplies on a math club card. What is 3i(4 − 2i)?
Milo's robot at 5 + 3i is multiplied by -2i: it turns and stretches. What is -2i(5 + 3i)?
Noah multiplies a grid map pin, -1 + 6i, by 4i. What is 4i(-1 + 6i)?

Add, subtract and multiply complex numbers. Every version has 10 questions, and the answer key prints on the second page.

I can add and subtract complex numbers by sliding: real with real, i with i.
I can multiply two complex numbers with four parts and turn i² into -1.
I can say what multiplying by i does to a point: a quarter turn counterclockwise.

Standard: N-CN.A.2

real part: The across number a in a + bi.

imaginary part: The up number b in a + bi.

slide: Adding a complex number moves a point across and up.

area model: A rectangle cut into four parts, one for each pair of terms.

i²: i × i, which equals -1.

Your child added the real numbers and the i numbers together as one (3 + 2i + 5 − 4i written as 6i).

Your child added the parts but dropped a minus sign.

Your child subtracted only the first part of the second number.

Ask: which numbers go across, and which go up?

Ask: which parts of these numbers are negative?

Ask: what does the minus in front of the brackets do to the i part?

What is the most common mistake with add, subtract and multiply complex numbers?

Your child added the real numbers and the i numbers together as one (3 + 2i + 5 − 4i written as 6i).

How can I help my child with add, subtract and multiply complex numbers?

Ask: which numbers go across, and which go up?

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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