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anonymous

  • one year ago

I need someone to explain this lesson to me. Be patient while I write the problem.

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  1. anonymous
    • one year ago
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    Ok so it is walking me through the steps to solve for x \[\sqrt{x+21}-3=\sqrt{x}\]

  2. anonymous
    • one year ago
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    Here are the steps:\[\sqrt{x+21}=3+\sqrt{x}\] \[x+21=9+6\sqrt{x}+x\] \[12=6\sqrt{x}\] \[\sqrt{x}=2\] \[x=4\]

  3. anonymous
    • one year ago
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    The 2nd step is the one I didn't understand?\[x+21=9+6\sqrt{x}+x\]

  4. UsukiDoll
    • one year ago
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    ahhhh... they squared both sides.

  5. UsukiDoll
    • one year ago
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    because we want x... no x^2 stuff square root of x just x so we square both sides \[(\sqrt{x+21})^2=(3+\sqrt{x})^2\]

  6. anonymous
    • one year ago
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    Ok but wouldn't that leave us with \[x+21=9+x\]

  7. UsukiDoll
    • one year ago
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    the left side is correct.. the right one requires expansion

  8. UsukiDoll
    • one year ago
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    \[(\sqrt{x+21})(\sqrt{x+21}) = (3+\sqrt{x})(3+\sqrt{x})\]

  9. UsukiDoll
    • one year ago
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    so square root x square root is just whatever is in the square root so x+21 = (use foil method )

  10. anonymous
    • one year ago
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    Ohhh Ok I get it thank you because the OI of FOIL add together to get the \[6\sqrt{x}\] thank you

  11. UsukiDoll
    • one year ago
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    yup

  12. UsukiDoll
    • one year ago
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    then what they did was shift that x to the left to eliminate it and the 9 is shifted to the left

  13. UsukiDoll
    • one year ago
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    then divide both sides by 6 afterwards square both sides again and x = 4

  14. anonymous
    • one year ago
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    Yeah I get it thanks I am really liking this site it's helpin me out a lot

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