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anonymous

  • one year ago

I have a question about the slope.... In the slope formula y=mx+b what is the difference between the y and the b and how do I know when to plug it in to the y or b?

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  1. Nnesha
    • one year ago
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    b is y-intercept a point where line cross y-axis(there would be only one ) y = just y-coordinate you don't need to plug anything for y

  2. anonymous
    • one year ago
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    Example problem: Line A has slope of -5/3 and passes through the point (-2,7). WHat is the x-intercept of line A?

  3. Nnesha
    • one year ago
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    yes y=mx+b so replace m with -5/3 y=-5/3x+b now you have x y value (-2,7) x=-2 y=7 substitute x and y for their solve for b(y-intercept )

  4. anonymous
    • one year ago
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    I just don't understand what to plug into the y or b.... like if they ask it passes through the line then what do i do? use it for the y or b?

  5. Nnesha
    • one year ago
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    x-intercept is a point where line cross the x-axis when y =0 after you find y-intercept substitute y for 0

  6. anonymous
    • one year ago
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    Like what are some examples of when i have to use it for y or b? what do they have to say for me to know where to replace it?

  7. Nnesha
    • one year ago
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    when they say passes through the points (x,y) then you have to find b

  8. anonymous
    • one year ago
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    so replace the b with the number they say it passes through the points?

  9. anonymous
    • one year ago
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    or the y

  10. Nnesha
    • one year ago
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    replace with y not b (b is y-intercept )

  11. anonymous
    • one year ago
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    hmmm okay

  12. Nnesha
    • one year ago
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    here is an example slope =2 passes through (4,3) \[\huge\rm \color{reD}{y}=mx+b\]\[(4,\color{ReD}{3})\]

  13. anonymous
    • one year ago
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    So in what cases do i replace the b (y-intercept) what kind of problems do they have to ask for

  14. Nnesha
    • one year ago
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    then statement would be like this slope is 3 and ***Y-INTERCEPT =5

  15. Nnesha
    • one year ago
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    they would use the *y-intercept ) word

  16. anonymous
    • one year ago
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    hmmm okay

  17. phi
    • one year ago
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    maybe this helps??: y = 3x + 2 is a formula to "find y" if you are told x. you then put the x and y together as a package (x,y) for example, if x is 1, y will be 5 (do you see how?) and (1,5) is the "package" which is just a way to say the point (1,5) is on the line. does that part make any sense?

  18. phi
    • one year ago
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    the next idea is we can (in theory) find all the points on the line using its formula that can be useful and the reason we want a formula rather than a long boring list of (x,y) pairs

  19. anonymous
    • one year ago
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    hmmmm i mean thats easy i'm just hving a hard time understand when to substitute the y or b

  20. Nnesha
    • one year ago
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    |dw:1439238885626:dw| i know why you r confused but y-intercept is the specific point where line cross the y-axis which is also one of the y value but they will always use the y-intercept word for b

  21. phi
    • one year ago
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    you will get the idea... but I want to make sure you got the basic idea the next idea is how do we find the formula for a line? it turns out you need just two points on the line, and there is a way to do that.

  22. anonymous
    • one year ago
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    what if they don't specifically use the term y-intercept like how will i know to plug what in where?

  23. phi
    • one year ago
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    as you know, the formula for a line is y= m x + b where m is the slope and b is the "y-intercept" if you are given two points, they you know how to find the slope, right ?

  24. anonymous
    • one year ago
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    2 points like (5, 2)? yea then just plug in 5 to x and 2 to b right?

  25. Nnesha
    • one year ago
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    when they say given points where (3,5) where first number represent x-coordinate and and 2nd number represent the y-coordinate (NOT y-intercept )

  26. Nnesha
    • one year ago
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    y-coordinate =y y-intercept = b

  27. phi
    • one year ago
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    **2 points like (5, 2)? *** oooh! no! a point is (x,y) pair. (5,2) is one point. to find it, you go over 5 and up 2 to get to it.

  28. phi
    • one year ago
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    two points would be for example (1,3) and (4,4)

  29. anonymous
    • one year ago
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    so then 3=m(1)+b?

  30. phi
    • one year ago
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    yes, you can do that. but the first step is to find m (which we can do) change in y divided by change in x what do you get for m ?

  31. anonymous
    • one year ago
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    y2-y1/x2-x1

  32. phi
    • one year ago
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    yes, and for (1,3) and (4,4) what do you get for m?

  33. anonymous
    • one year ago
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    1/3

  34. phi
    • one year ago
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    ok. now we go back to the equation 3=m(1)+b and put in m= 1/3 3= 1/3 * 1 + b or 3= 1/3 + b sorry about the ugly numbers... but we can solve for b by adding -1/3 to both sides.

  35. phi
    • one year ago
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    you get b= 3 - 1/3 or 8/3 notice if we start with y = 1/3 x + b and put in the other point (4,4) 4 = 1/3 * 4 + b 4= 4/3 + b 4- 4/3 = b and b= 12/3 - 4/3 = 8/3 we get the same b

  36. anonymous
    • one year ago
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    yea i know about that u'll always get the same solution no matter which u plug in

  37. Nnesha
    • one year ago
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    \(\color{blue}{\text{Originally Posted by}}\) @yomamabf 2 points like (5, 2)? yea then just plug in 5 to x and 2 to b right? \(\color{blue}{\text{End of Quote}}\) also when the statement is *passes through point * that means solve for b easy way to memorize it ;)

  38. phi
    • one year ago
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    if you are given two points, you find the equation of the line by 1) find the slope 2) use either (x,y) pair to replace the x and y in the equation with numbers and solve for b does that sound ok?

  39. phi
    • one year ago
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    if you are told the y-intercept is 3 (for example) that is the same info as telling you that (0,3) is a point on the line (y-intercept is the y value when x is 0)

  40. anonymous
    • one year ago
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    hmmm okay got it

  41. phi
    • one year ago
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    say the problem was: slope is 3 y intercept is 3 what is the equation? two ways to do it: y = mx + b we are told m is 3, so y= 3x + b (0,3) is a point on the line 3= 3*0 + b 3 = b so y= 3x+3 the other way: replace m with 3 (the slope), and replace b with 3 (the y-intercept) y = 3x+3

  42. anonymous
    • one year ago
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    yea i was thinking the latter

  43. phi
    • one year ago
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    yes, but it is good to see how to do it the first way. It always helps to see problems solved in different ways.

  44. anonymous
    • one year ago
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    hmmm okay got it

  45. anonymous
    • one year ago
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    thank you!!!!

  46. phi
    • one year ago
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    the first way is how you do it for any point on the line. (0,3) is just an easy point (because it tells us what b is ... or multiplying x by 0 is easy)

  47. anonymous
    • one year ago
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    okay i'm going to try to find another problem and see if i can do it by myself i need practice =(

  48. phi
    • one year ago
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    if you get lost, post the problem

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