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anonymous

  • 5 years ago

multiply: (1+2i)(2-i)

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  1. anonymous
    • 5 years ago
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    i am so lost on where to start with this problem

  2. anonymous
    • 5 years ago
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    this is 8th grade math right?

  3. anonymous
    • 5 years ago
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    intermediate algebra. would i answer it the same if it was 'x' instead of 'i'

  4. watchmath
    • 5 years ago
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    You just apply the distributive property \(1\cdot 2+1\cdot (-i)+2i\cdot2+2i\cdot (-i)\)

  5. anonymous
    • 5 years ago
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    Just foil it out like you would normally (treat the i kinda like a variable) and just remember that if you have an \(i^2\) that equals -1

  6. anonymous
    • 5 years ago
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    oh okay!! thanks! i wasnt sure if i just fouil like normal. the "i" threw me off!

  7. anonymous
    • 5 years ago
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    don't be scared of letters. They're actually much easier to work with than numbers because you don't have to plug them into your calculator ;)

  8. anonymous
    • 5 years ago
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    thank you. i got 2-1i+4i-2i so far

  9. anonymous
    • 5 years ago
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    2+3i-2i as the answer

  10. watchmath
    • 5 years ago
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    \(2-1i+4i-2i^2\). Now you can use \(i^2=-1\)

  11. anonymous
    • 5 years ago
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    2+3i-2i^2 ..which would be 2+3i+2

  12. watchmath
    • 5 years ago
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    good! you can combine 2+2 as well

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