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Algebra2

posted by on .

Help?
I Kind of understand this , but still I am stuck.

1. (2+4i)/3-i

2. 3√-50 + -72

3.(-4+√-15)^2

4.-4+√-20

5.7√-2(-4√-3)

  • Algebra2 - ? - ,

    we kind of don't know where you get stuck. Show us what you got, and we can help you work it the rest of the way.

  • Algebra2 - ,

    1. I got 6+3/10
    but i don't believe that's the correct answer.

    2. i got √21.21+√-8.49

    3. i got 34+14√10i

    4. i got -1+√5i

  • Algebra2 - ,

    #1: (2+4i)/(3-i)
    = (2+4i)(3+i) / (3-i)(3+i)
    = (6 + 12i + 2i + 4i^2) / (3^2 - i^2)
    = (6 + 14i - 4) / (9+1)
    = (2+14i)/10
    = 1/5 + 7/5 i

    #2: 3√-50 + -72
    3√50 i - 72
    3*5√2 i - 72
    -72 + 15√2 i
    in this kind of exercise, there's no call to approximate √ values with decimals. The √ is exact; the decimals are only an approximation.

    #3: (-4+√-15)^2
    = (-4 + √15 i)^2
    = (-4)^2 + 2(-4)(√15 i) + (√15 i)^2
    = 16 - 8√15 i - 15
    = 1 - 8√15 i

    #4: -4+√-20
    = -4 + √20 i
    = -4 + 2√5 i

    #5: 7√-2(-4√-3)
    = 7(√2 i)(-4)(√3 i)
    = -28 √6 i^2
    = 28√6

    Does that help? Just take these things step by step, keeping track of the i's and signs.

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