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yociyoci

  • 3 years ago

Can someone guide me through inequality questions? i) 15-2y-y^2<0 ii) 20x-4x^2-25>0

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  1. Mertsj
    • 3 years ago
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    \[y^2+2y-15>0\]

  2. yociyoci
    • 3 years ago
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    so now, (y-3)(y+5)>0? and y>-5 or y<3?

  3. Mertsj
    • 3 years ago
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    The first part is right. If you multiply two factors and get a positive result, then both factors must be positive or both factors must be negative.

  4. Mertsj
    • 3 years ago
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    |dw:1361936550944:dw|

  5. Mertsj
    • 3 years ago
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    So we see that the solution is y <-5 or y>3

  6. yociyoci
    • 3 years ago
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    oh, alright. What about the second question? I got suck at (2x-3)^2 > 0

  7. Mertsj
    • 3 years ago
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    \[4x^2-20x+25<0\] \[(2x-5)(2x-5)<0\]

  8. yociyoci
    • 3 years ago
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    opps, I was looking at a different one. Yes, I got to (2x-5)^2<0

  9. Mertsj
    • 3 years ago
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    |dw:1361936871505:dw|

  10. Mertsj
    • 3 years ago
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    Oh, it will never be less than 0 but of course we already knew that a real number raised to the second power will always be positive or 0 and never less than 0

  11. yociyoci
    • 3 years ago
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    So there will be no solution in this case, but what if it is (2x-5)^2 > 0? Will this work?

  12. Mertsj
    • 3 years ago
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    Yes. Then it would be all real numbers except 0

  13. yociyoci
    • 3 years ago
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    Alright! Thank you so much!

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