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    I know its simple but please see attatched.
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    That brackets thing is minor. You have the same answer. They only did that because without the brackets you can't tell all the bits that come inside their square root as the line doesn't go all the way across, but it clearly does with what you have written.

    If they just did √BLAH, you dont know if thats  \sqrt B \cdot LAH or  \sqrt{BL} \cdot AH or what. By putting it in the brackets just shows you that all of that comes inside the square root.

    Regarding the 9 thing:

     y = 3\sqrt{4x - x^2}

    To get rid of the square root sign, you square both sides, i.e

     y^2 = (3 \sqrt{4x - x^2})^2

    From here you see that

     (3\sqrt{4x - x^2})^2 = 3^2 \cdot (\sqrt{4x - x^2})^2 = 9(4x - x^2)
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    The extra brackets just come from their square root sign which doesn't stretch all the way over like yours does: you both have written effectively the same thing
    Unless you mean a different pair of brackets?

    The 9 comes from the squaring.
    If you have z=xy, then z2=x2y2
    So if:
    y=3\sqrt{4x-x^2}
    Then:
    y^2=3^2\ .\ (4x-x^2)
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    (Original post by claret_n_blue)
    That brackets thing is minor. You have the same answer. They only did that because without the brackets you can't tell all the bits that come inside their square root as the line doesn't go all the way across, but it clearly does with what you have written.

    If they just did √BLAH, you dont know if thats  \sqrt B \cdot LAH or  \sqrt{BL} \cdot AH or what. By putting it in the brackets just shows you that all of that comes inside the square root.

    Regarding the 9 thing:

     y = 3\sqrt{4x - x^2}

    To get rid of the square root sign, you square both sides, i.e

     y^2 = (3 \sqrt{4x - x^2})^2

    From here you see that

     (3\sqrt{4x - x^2})^2 = 3^2 \cdot (\sqrt{4x - x^2})^2 = 9(4x - x^2)

    (Original post by placenta medicae talpae)
    The extra brackets just come from their square root sign which doesn't stretch all the way over like yours does: you both have written effectively the same thing
    Unless you mean a different pair of brackets?

    The 9 comes from the squaring.
    If you have z=xy, then z2=x2y2
    So if:
    y=3\sqrt{4x-x^2}
    Then:
    y^2=3^2\ .\ (4x-x^2)

    thank you for taking time to explain that rep for you both
 
 
 
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