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Math Help - gradients and y-intecept

  1. #1
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    gradients and y-intecept

    This question may be a bit vague but considering i cant draw the graph i hope someone can still help

    I need to find the gradient and y-intercept of a line given, than i need to write the equation of the line.

    Now am i correct in saying the y-intercept is where the line crosses on the y point?

    If so than it crosses at -1

    so how do i than find the gradient if that is all im given?
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  2. #2
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    Quote Originally Posted by BsMummy View Post

    Now am i correct in saying the y-intercept is where the line crosses on the y point?
    Let's call it the y-axis, do you have the point where your line crosses the x-axis?

    This can help you find the gradient
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  3. #3
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    Quote Originally Posted by BsMummy View Post
    This question may be a bit vague but considering i cant draw the graph i hope someone can still help

    I need to find the gradient and y-intercept of a line given, than i need to write the equation of the line.

    Now am i correct in saying the y-intercept is where the line crosses on the y point?

    If so than it crosses at -1

    so how do i than find the gradient if that is all im given?
    Yes, you are correct about the y-intercept. In order to find the gradient of a line you need two points. If you know the y-intercept, then you have the point (0,-1). But you have to have another point to find the gradient. What other information are you given? There must be more. Are you given a graph of the line?
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  4. #4
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    Quote Originally Posted by pickslides View Post
    Let's call it the y-axis, do you have the point where your line crosses the x-axis?

    This can help you find the gradient

    The line crosses the x-axis at 4
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  5. #5
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    Quote Originally Posted by adkinsjr View Post
    Yes, you are correct about the y-intercept. In order to find the gradient of a line you need two points. If you know the y-intercept, then you have the point (0,-1). But you have to have another point to find the gradient. What other information are you given? There must be more. Are you given a graph of the line?

    would finding the x-axis help? if so that would be 4

    so now i have (0,-1) and (0,4)

    is that all i will need to find the gradient?

    yes i am given a graph of the line but i dont know how to but that graph up on here!
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  6. #6
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    Quote Originally Posted by BsMummy View Post

    so now i have (0,-1) and (0,4)
    No, you really have (0,-1) and (4,0)

    the gradient m = \frac{y_2-y_1}{x_2-x_1}

    where (0,-1) = (x_1,y_1) and (4,0) = (x_2,y_2)
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  7. #7
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    okay so i have worked out that the gradient is .5 or 1/2 - but i worked that out by looking at the graph and counting how many sqaures i went up from the y intercept to the x intercept

    so now that i have the gradient at .5 or 1/2 how do i write the equation of the line?
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  8. #8
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    Quote Originally Posted by BsMummy View Post
    okay so i have worked out that the gradient is .5 or 1/2 - but i worked that out by looking at the graph and counting how many sqaures i went up from the y intercept to the x intercept

    so now that i have the gradient at .5 or 1/2 how do i write the equation of the line?
    The general form is y=mx+b. So the line will have the equation y=\frac{1}{2}x+b where b is the y-intercept. Since b=-1, the line is y=\frac{1}{2}x-1
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  9. #9
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    okay i used the way to find the gradient that pickslides gave and now im getting 1/4 - which im thinking would be the right answer since im no maths genious!
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  10. #10
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    Quote Originally Posted by adkinsjr View Post
    The general form is y=mx+b. So the line will have the equation y=\frac{1}{2}x+b where b is the y-intercept. Since b=-1, the line is y=\frac{1}{2}x-1

    thankyou - i will just change the 1/2 to a 1/4 since i think that is the gradient - thanks Heaps to you and Pickslides
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  11. #11
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    Quote Originally Posted by BsMummy View Post
    thankyou - i will just change the 1/2 to a 1/4 since i think that is the gradient - thanks Heaps to you and Pickslides
    Yep.
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