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Math Help - i am lousy at math~ plz help mi solve!

  1. #1
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    i am lousy at math~ plz help mi solve!

    [IMG]D:\Documents and Settings\fang\My Documents\Scan0002.jpg[/IMG]


    OPS~ how to put picture?!?!?!?!
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by xiaoz
    [IMG]D:\Documents and Settings\fang\My Documents\Scan0002.jpg[/IMG]


    OPS~ how to put picture?!?!?!?!
    When creating a post scroll down past the text editor window,
    you will see a button marked manage attachments, click on
    it and it will allow you to upload a jpg attachment.

    RonL
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  3. #3
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    kk. thxz .. here is questions i dunno.. i am confuse at math tis yr!!
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  4. #4
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    they say canot use calculator.. i dunno how to do the working.. my math fail badly too.. HELP!
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  5. #5
    Grand Panjandrum
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    1.a Evaluate:

    \sqrt{1\frac{11}{25}}

    first change what is under the root symbol from a mixed number to an
    improper fraction:

    <br />
\sqrt{1\frac{11}{25}}=\sqrt{\frac{36}{25}}=\frac{ \sqrt {36}}{\sqrt{25}}<br />

    You should now be able to complete this without a calculator as
    both 36 and 25 are perfect squares.

    RonL
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  6. #6
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    o.. i find out the answer liao... is 6 over 5.. thx!!

    1b.. explain plz..
    Last edited by xiaoz; June 6th 2006 at 09:51 PM.
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  7. #7
    Grand Panjandrum
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    1.b Evaluate \sqrt{2120} without a calculator given that

    \sqrt{2.12}=1.456 and \sqrt{21.2}=4.004.

    We want to write 2120 as a product of a square and one of
    the number we are given the square root of. Now:

    2120=1000 \times 2.12,

    and

    2120=100 \times 21.2.

    1000 is not the square of an integer, but 100=10^2. So we can write:

    <br />
\sqrt{2120}=\sqrt{100 \times 21.2}=\sqrt{100}\times \sqrt{21.2}<br />
.

    RonL
    Last edited by CaptainBlack; June 6th 2006 at 11:22 PM.
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  8. #8
    Grand Panjandrum
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    1.c Evaluate without a calculator:

    <br />
\left(-\frac{1}{216}\right)^{-2/3}<br />

    Now:

    <br />
\left(-\frac{1}{216}\right)^{-2/3}=\frac{1}{(-\frac{1}{216})^{2/3}}<br />
<br />
=\frac{1}{((-\frac{1}{216})^{1/3})^2}=\frac{1}{((-\frac{1}{(216)^{1/3}}))^2}<br />

    Now this can be evaluated from the innermost brackets outward, as 216 is
    a perfect cube (of a small number which you can find by trial and error).

    RonL
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  9. #9
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    Hello,xiaoz!

    Here's #6 . . .

    6(a) Solve the inequality: 5 \;< \;6x - 13 \;< \;7
    We have: . 5 \;< \; 6x - 13 \;< \;7

    Add 13 to each side: .  18 \:< \:6x \:< \:20

    Divide by 6: . 3 \;< \;x \;< \;\frac{10}{3}

    (b) Find a fraction x such that: \frac{7}{11}\;<\:x\:<\:\frac{8}{11}
    There are several ways to solve this problem.

    (1) To find a number between two given numbers, average the numbers.
    . . . x\;=\;\frac{\frac{7}{11} + \frac{8}{11}}{2} \;=\;\frac{15}{22}

    (2) Convert to decimals: \begin{array}{cc}\frac{7}{11} = 0.63\hdots \\ \frac{8}{11} = 0.72\cdots\end{array}
    Then let x be any decimal between 0.64 and 0.72

    For example: . x\:=\:0.65\:=\:\frac{65}{100} \:= \:\frac{13}{20}

    (c) If x^{2y} = 5, find the value of 2x^{6y} - 4
    Change the first expression into the second, step by step.

    We have: .  x^{2y}\:=\:5

    Cube both sides: . (x^{2y})^3\:=\:5^3\quad\Rightarrow\quad x^{6y}\:=\:125

    Multiply by 2: . 2x^{6y}\;=\;250

    Subtract 4: . 2x^{6y} - 4 \:= \:246
    Last edited by Soroban; June 7th 2006 at 03:52 AM.
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  10. #10
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    Unhappy

    thxz.. 1b i undersyand.. 1c i dunno still... 6c the last part.. the mutiply by 2 de.. got the power still can mutiply?? how about question 2a and b.. explaint plz.. thxz
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  11. #11
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    Hello, xiaoz!

    Let me give 1(c) a try . . .

    1(c) Simplify: \left(-\frac{1}{216}\right)^{-\frac{2}{3}}
    Did you know that a negative exponent on a fraction flips the fraction?
    . . \left(\frac{a}{b}\right)^{-n}\;=\;\left(\frac{b}{a}\right)^n

    We have: \left(-\frac{1}{216}\right)^{-\frac{2}{3}}\:=\: (-216)^{\frac{2}{3}}


    We know that: -216 = (-6)^3

    So we have: [(-6)^3]^{\frac{2}{3}}\;=\;6^{(3\cdot\frac{2}{3})} \;=\;6^2\;=\;36
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  12. #12
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    Red face

    woow..i did not know about tt formula.. hahax.. thxz to u.. i understand liao..
    other question.. plz help.. explain to mi..
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  14. #14
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    Unhappy

    kk.. thxz all...now plz help mi wif question 2 , 3 , 4 , 5
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