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Math Help - Graph work again!

  1. #1
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    Exclamation Graph work again!

    im stuck on this question:
    a. draw the graph of y=3x-6
    b. draw the inverse aswell
    c. what is y=3x and its inverse symmetrical about?
    d. what do you notice about the line of symmetry?
    im stuck on c and d can someone(if possible) pleez explain it in SIMPLE language coz im only in yr9!
    thankyou
    Last edited by help_me; October 8th 2007 at 10:47 AM.
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by help_me View Post
    im stuck on this question:
    a. draw the graph of y=3x-6
    to draw a line, all you need are two points. the x- and y-intercepts are usually good points, especially since you only have to find one of them (the y-intercept is given by the lone constant, so we don't have to calculate it).

    for the x-intercept, set y = 0

    => 0 = 3x - 6
    => x = 2

    thus, our y-intercept is (0,-6) and our x-intercept is (2,0)

    so plot those points on a pair of axis and draw a straight line through them and you're done. see below

    b. draw the inverse aswell
    to find the inverse function of y = f(x), we switch x and y and solve for y.

    thus for the inverse of y = 3x - 6, we solve: x = 3y - 6 for y.

    => y = (1/3)x + 2 is the inverse function.

    graph this the same way i did the other.

    c. what is y=3x and its inverse symmetrical about?
    for any graph that has an inverse, the graph and it's inverse is symmetrical about the line y = x.

    d. what do you notice about the line of symmetry?
    i leave this question to you. after drawing the graphs, you tell me
    Attached Thumbnails Attached Thumbnails Graph work again!-line.jpg  
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  3. #3
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    Smile oh...........

    thank you so much for explaining it so clearly!
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  4. #4
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    for the x-intercept, set y = 0

    => 0 = 3x - 6
    => x = 2


    That's cool and easy! I never knew that.
    I always plugged in coordinates (1,1) to find the 'y' intercept and for some reason I don't remember what I did next.
    It wasn't as easy as that though.
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