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vivalakoda

  • 2 years ago

Solve for x?

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  1. vivalakoda
    • 2 years ago
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    \[-4\sqrt{x+9}=20 \]

  2. AntarAzri
    • 2 years ago
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    sqrt(x+9)=-(20/4)

  3. vivalakoda
    • 2 years ago
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    I know how to solve is, I'm just not sure how to get rid of the -4 in the front of the radical.

  4. Ladyalice25
    • 2 years ago
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    you need to remove the square from x+9 the way you do that is by squaring both side and you end up with x+9=-(20/4)^2. then solve from there.

  5. AntarAzri
    • 2 years ago
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    yes that 's it

  6. Ladyalice25
    • 2 years ago
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    x+9=-20/4)^2. -20/4^2 = -25 then take -25 subtract 9. you will get the answer of x=-34

  7. dpaInc
    • 2 years ago
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    it's easy to see that this has NO SOLUTION: (-4)*(-5) = 20 so that means: \(\large -4\sqrt{x+9}=20 \rightarrow \sqrt{x+9}=-5\) \(\large \sqrt{x+9}=-5\) which has no solution because the left side is always positive but the right side is negative

  8. vivalakoda
    • 2 years ago
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    Can't you just square both sides to get rid of the square root, then solve like an equation?

  9. dpaInc
    • 2 years ago
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    yes you can try to do that... it's one technique you should try to solve it. but why continue when you know this is an impossible equation to solve?

  10. dpaInc
    • 2 years ago
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    not impossible, no solution... if you do solve it, the solution is an extraneous solution....

  11. vivalakoda
    • 2 years ago
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    If according to your answer it is √x+9 = -5 then you'd square both sides to have: x+9 = -25 subtract 9 from both sides and get -16 as x?

  12. AntarAzri
    • 2 years ago
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    Difficult equation in history

  13. dpaInc
    • 2 years ago
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    squaring both sides you get positive 25

  14. vivalakoda
    • 2 years ago
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    Oh, that's right thanks so then x+9=25 subtract 9 then positive 16?

  15. dpaInc
    • 2 years ago
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    yes... now let's see if the solution of x=16 works....

  16. AntarAzri
    • 2 years ago
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    no no no no =-20

  17. AntarAzri
    • 2 years ago
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    that's wrong

  18. dpaInc
    • 2 years ago
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    \(\large (-4)(\sqrt{x+9})=20 \) \(\large (-4)(\sqrt{\color {red}{16}+9})=20 \) \(\large (-4)(\sqrt{\color {red}{25}})=20 \) \(\large -4 \cdot 5 = 20 \) \(\large -20=20 \) ???? not a true statement

  19. dpaInc
    • 2 years ago
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    so the solution of x=16 is extraneous and not really a solution.

  20. AntarAzri
    • 2 years ago
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    solution \[\left| -4 \right|\]

  21. AntarAzri
    • 2 years ago
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    suggestion hhhh

  22. dpaInc
    • 2 years ago
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    @AntarAzri , what's the solution?

  23. AntarAzri
    • 2 years ago
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    \[\left| -4 \right|\]

  24. dpaInc
    • 2 years ago
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    \(\large (-4)(\sqrt{x+9})=20 \) \(\large (-4)(\sqrt{|-4|+9})=20 \) \(\large (-4)(\sqrt{4+9})=20 \) \(\large (-4)(\sqrt{13})=20 \) x=|-4| doesn't seem to work. That's not a solution.

  25. vivalakoda
    • 2 years ago
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    my oh my I have headaches because of this problem..

  26. AntarAzri
    • 2 years ago
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    no no i dont mean the x |−4|=4

  27. dpaInc
    • 2 years ago
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    ok. whatever... my answer stands... NO SOLUTION to the equation: \(\large (-4)(\sqrt{x+9})=20 \) \)

  28. AntarAzri
    • 2 years ago
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    \[(\left| -4 \right|)(\sqrt{16+9})=20\]

  29. dpaInc
    • 2 years ago
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    here's wolframs answer: http://www.wolframalpha.com/input/?i=solve+-4*sqrt%28x%2B9%29%3D20

  30. AntarAzri
    • 2 years ago
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    good

  31. AntarAzri
    • 2 years ago
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    http://www.wolframalpha.com/input/?i=solve+|%E2%88%924|*sqrt%28x%2B9%29%3D20

  32. vivalakoda
    • 2 years ago
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    ?

  33. dpaInc
    • 2 years ago
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    if u don't understand my answer and expanation maybe someone else can give u a better answer... i will not argue my point further....

  34. AntarAzri
    • 2 years ago
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    Do we agree that it can not be the root of a negative number gives a positive number ?

  35. vivalakoda
    • 2 years ago
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    I'll see what my teacher says when she grades it. Thanks for your time

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