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    Multiply Complex Numbers

    How to multiply complex numbers, complex conjugates

    To multiply to complex numbers such as (4+5i )(3+2i) , you can treat each one as a binomial and apply the FOIL method to find the product.
      FOIL
    • multiply the firsts 4 ×3 = 12
    • multiply the outers 4 × 2i = 8 i
    • multiply the inners 5i ×3 = 15i
    • multiply the lasts 5 i × 2 i = 10i 2= -10
    • Then add:  12 + 4i + 15i -10 = 2 +23i
     Complex Conjugate 
    Complex conjugates are any pair of complex number binomials that look like the following pattern: (a + bi) & (a-bi)
      Here are some specific examples. Note that the only difference between the two binomials is the sign.
    • (3 - 2i )( 3 +2i)
    • (5 + 12i )( 5 - 12i)
    • (7 - 33 i )( 7 +33i)

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