Algebra 1

This is a discussion on Algebra 1 within the A Brief History of Cprogramming.com forums, part of the Community Boards category; I have this problem. In my book it doesnt have any examples of this type of problem. Please help! Code: ...

  1. #1
    i dont know Vicious's Avatar
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    Question Algebra 1

    I have this problem. In my book it doesnt have any examples of this type of problem. Please help!

    Code:
    Radical Equations
         _________     _______
       \/ x^2 + 2x = \/ 10 - x
    What is C++?

  2. #2
    Registered User JasonLikesJava's Avatar
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    Square both sides of the equations and then you've got a quadratic equation.

    x^2 + 2x = 10 - x
    x^2 + 3x - 10 = 0
    (x+5)(x-2) = 0
    x = -5 or 2
    Last edited by JasonLikesJava; 06-04-2002 at 10:21 AM.
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    -_-;

    Uh... can you explain?

    How did 2x turn into 3x?

    (x+5)(x-2) = 0 ? where did that come from?
    What is C++?

  4. #4
    Confused Magos's Avatar
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    How did 2x turn into 3x?
    He "moved" it from the right side to the left side. Look at this equation:

    3 = 2 + 1

    That is the same as:

    3 - 1 = 2

    You can add, subtract, multiply and divide with whatever you want only if you do the same on both sides. What Jason did was add x on both sides.

    2x + x turned into 3x
    and -x + x turned into 0 (nothing)
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    so -2 and 5 are factors of 10. Which is number c.

    the sum of the factors of c have to equal b wich is 3.

    -2 + 5 = 3..

    Did I get it?
    What is C++?

  6. #6
    i dont know Vicious's Avatar
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    okay... now lets say I have a problem like this?

    Code:
       ______
    \/ x + 6 = x + 4
    that has a radical expresion on just one side... can I work it like this?

    x + 6 = x^2 + 16

    What is C++?

  7. #7
    Confused Magos's Avatar
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    (x+5)(x-2) = 0 ? where did that come from?
    x^2 + 3x - 10 = 0
    Original equation

    x^2 + (2 * (3 / 2)) x - 10 = 0
    2 * (3 / 2) is the same as 3. Multiply by 2 and then divide with 2 and you get the same number as before

    x^2 + (2 * (3 / 2)) x + (3 / 2)^2 - (3 / 2)^2 - 10 = 0
    First you add (3 / 2)^2, then you subtract it, so you haven't changed the value of the equation

    (x + (3 / 2))^2 - (3 / 2)^2 - 10 = 0
    Using the rule (a + b)^2 = a^2 + 2 * a * b + b^2 (sorry, don't know the english name of it ) you can change the first three terms of step 3 into the blue coloured part in this step

    (x + (3 / 2))^2 - (9 / 4) - (40 / 4) = 0
    3^2 equals 9 and 2^2 equals 4. I also change 10 into (40 / 4), which is the same thing

    (x + (3 / 2))^2 - (49 / 4) = 0
    -9 - 40 equals -49

    (x +(3 / 2))^2 = (49 / 4)
    Add (49 / 4) to both sides (see my previous post)

    x + (3 / 2) = +/- sqrt( 49 / 4 )
    Take the square root of both sides. Notice the +/-, since both a and -a is a^2 when squared (is this a real word?).

    x = -(3 / 2) +/- (7 / 2)
    Subtract (3 / 2) from both sides

    x1 = -(10 / 2) = -5
    x2 = (4 / 2) = 2
    Since we have a +/-, x have two values (unless it's a double root). -3 - 7 is -10, and -3 + 7 is 4

    If you put in any of these values in (x + 5)(x - 2) = 0, you see that the left side has the value 0, and the equation is correct.

    Hope this helps a little. Algebra can be tough sometimes .
    Last edited by Magos; 06-04-2002 at 11:06 AM.
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    ............................................

    (Vicious is suffering from a braon freeae that Magos has caused him)
    What is C++?

  9. #9
    Confused Magos's Avatar
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    Originally posted by Vicious
    can I work it like this?

    x + 6 = x^2 + 16
    No, the correct would be:

    x + 6 = (x + 4)^2

    x + 6 = x^2 + 2 * 4 * x + 4^2
    MagosX.com

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  10. #10
    Registered User JasonLikesJava's Avatar
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    I wasn't sure how much explaining to do since I wasn't sure at what level you were in in Algebra I.

    --edited--
    Last edited by JasonLikesJava; 06-04-2002 at 11:15 AM.
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  11. #11
    Registered User JasonLikesJava's Avatar
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    Once you get x^2 + 3x - 10 = 0 you can use the equation
    Code:
                         _________
    x = -b (+/-) \/ b^2 - 4ac
          --------------------------
                     2a
    Where a is what is in front of x^2 (1), b is what is in front of x (3) and c is -10
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    If you go flying back through time and you see somebody else flying forward into the future, it's probably best to avoid eye contact.

  12. #12
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    Thanks for your help..

    I guess I might can get through with Algebra before next school year starts
    What is C++?

  13. #13
    Registered User Dual-Catfish's Avatar
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    Try #math on DALnet if you need help with math

  14. #14
    Just because ygfperson's Avatar
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    if you like this wait until calculus.
    f(x) = x^3+2x^2+5x+3
    synthetic division, first and second derivatives, and all that fun stuff

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