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Simple high-school math problems

  1. Feb 8, 2007 #1
    Simple high-school math problems!!

    I really need some help!! I am pretty bad at math and am having an awful lot of trouble with my homework.

    1.) How do I graph by stating the x and y intercepts? How do I figure out what those are?

    ex. x + y = 7
    3x - 2y = 6

    2.) How do I graph using the slope intercept form (y = mx + b)?

    ex. y= -2x + 3
    y = x - 2

    3.) And lastly, how do I solve this question

    0.2(4n + 1) = 0.5(n-2)??
    !!!!!!!!! I just realized I posted this in the wrong forum. Sorry
     
  2. jcsd
  3. Feb 8, 2007 #2
    1) Start with the definition of the x and y intercepts. What do they mean and how do they help you graph?

    2) Look up the form y=mx+b to find out what m and b are, and learn how to find and use them.

    3) Have you used the distributive property before?

    The distributive property says that:

    [tex]a(b + c) = a*b + a*c[/tex]
     
  4. Feb 8, 2007 #3
    1) x-intercept when y=0
    y-intercept when x=0

    2) They are already in the y=mx + b form
    Say y=2x-3, then m=2 and b=-3
    that is, the gradient is 2 and the y intercept is at y=3 (since x=0, mx=0)
     
  5. Feb 9, 2007 #4

    Gib Z

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    Homework Helper

    ok dude, it seems like your only doing y=mx+b graphs right now.

    Since theres lines are always straight, we just get any 2 points and draw the line that connects them. any 2 are fine, but x and y ints are easiest to work out, because zeros easy to work with.
     
  6. Feb 10, 2007 #5
    To find the x-intercept, let y = 0 and solve the equation for x.
    To find the y-intercept, let x = 0 and solve the equation for y.

    In x + y = 7, both the x and y intercepts are 7.

    In 3x - 2y = 6, the x-intercept is 2, and the y-intercept is -3.


    In the equation y = mx + b, m is the slope and b is the y-intercept.

    With regard to y = -2x + 3, you already know that (0,3) is a solution, since 3 is the y-intercept. Simply substitute another value for either x or y, solve the equation, plot the point, and graph the line. This is no different than graphing any other linear equation.

    The same is true for y = x - 2. FYI, the coefficient of x is the slope, so in this case the slope is equal to 1.

    And lastly, how do I solve this question

    You solve it like any other equation. Start by removing the parenthesis by using the distributive property. This property states a(b + c) = ab + ac. So, your equation then becomes:

    0.8n + 0.2 = 0.5n - 1

    From here you can use the subtraction principle to cancel the 0.5n:

    0.3n + 0.2 = -1

    Use that principle again to cancel the 0.2:

    0.3n = -1.2

    Now use the division principle to solve for n:

    n = 4
     
  7. Feb 10, 2007 #6
    For the future, you should never post full solutions to homework problems.
     
  8. Feb 10, 2007 #7
    My bad, I'm new to this forum. Sorry about that.
     
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