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Math Help - graphing equations...

  1. #1
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    Question graphing equations...

    I am asked to graph this equation by plotting points;

    y=-x^2+4

    So far I have used these numbers to get the value of y

    x=0 y=4

    x=1 y=5

    x=2 y=8

    But the problem I am having is that if I keep on, the value for y gets further away from the first two points.

    If I use a negative number it obviously becomes a positive number....

    Could I multiply the entire equation by -1 so that the 4 becomes a negative?


    Many thanks in advance

    BTW, how do I create a space between the numbers so that when I post it doesn't look too awkward, or confusing??!??
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Morzilla View Post
    I am asked to graph this equation by plotting points;

    y=-x^2+4

    So far I have used these numbers to get the value of y

    x=0 y=4

    x=1 y=5

    x=2 y=8

    But the problem I am having is that if I keep on, the value for y gets further away from the first two points.

    If I use a negative number it obviously becomes a positive number....

    Could I multiply the entire equation by -1 so that the 4 becomes a negative?


    Many thanks in advance
    first off, your points are wrong. when the minus sign is outside the x^2, the answer is negative. there is a difference between -x^2 and (-x)^2. you were doing the latter, when the first is what is meant

    the points x = -2, -1, 0, 1, 2 are fine

    BTW, how do I create a space between the numbers so that when I post it doesn't look too awkward, or confusing??!??
    i don't know what you're referring to
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  3. #3
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    Quote Originally Posted by Jhevon View Post
    first off, your points are wrong. when the minus sign is outside the x^2, the answer is negative. there is a difference between -x^2 and (-x)^2. you were doing the latter, when the first is what is meant

    the points x = -2, -1, 0, 1, 2 are fine


    i don't know what you're referring to
    but wait, if I where to give -x^2 a value; -x^2= -2^2, would it not be 4, since two to the second power is four!?

    thanks
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Morzilla View Post
    but wait, if I where to give -x^2 a value; -x^2= -2^2, would it not be 4, since two to the second power is four!?

    thanks
    no. the answer would be -4. the minus sign is on the outside of the square, meaning, it is not affected by the squaring. the squaring only affects the x here

    now let's say we had x^2, and we plug in x = -2, then we would have (-2)^2 = +4. do you see the difference? the minus sign is in the brackets, so it is affected by the square
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    Quote Originally Posted by Jhevon View Post
    no. the answer would be -4. the minus sign is on the outside of the square, meaning, it is not affected by the squaring. the squaring only affects the x here

    now let's say we had x^2, and we plug in x = -2, then we would have (-2)^2 = +4. do you see the difference? the minus sign is in the brackets, so it is affected by the square

    So ,it does not matter what number we plug in -x^2, the number will still be a negative number then?

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  6. #6
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Morzilla View Post
    So ,it does not matter what number we plug in -x^2, the number will still be a negative number then?

    correct, because x^2 will always be non-negative, but the minus sign in front negates it, so you end up with a non-positive number
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  7. #7
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    ahhhhh, ok THANK YOU THANK YOU VERY MUCH!!!!

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