y = mx + b question

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ginny1029

Junior Member
Joined
Apr 25, 2009
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Can so one please explain b?
i understand that y is for the second number in an ordered pair and x is the first number
m is for the rise over run but i dont get the b part

thanks lol
 
i do on a grid thats where your starting place is ex. y=1/3x+ -5 you would go to a grid and start at -5 then go up one over three, up one over three ect. that would be your points to make your line. if that doesnt help be more specific, like do you need to find b in an equation or what? im just tryin to help so no hard feelings please.
 
Hard Feelings? im just happy someone is answering me lol

here is what started it

solve each system of equations by graphing, If there is no solution or an infinite number of solutions state this

y = -2x + 5
x + y = 4

my class notes say to use the y = mx + b formula but I dont get it quite yet
 
y = -2x + 5
x + y = 4 this becomes y=-x+4 (i brought the "x" over then it became "negative") then graph each. do you no how?
 
i think the graphing would be ok i just dont get what numbers to use or how to use the formula
to get the numbers to use
 
ginny1029 said:
… just dont get what numbers to use [to be able to plot points to graph these lines] or how to use the formula to get the numbers …
Click to expand...


You get to pick values for x, followed by using the formula to find the corresponding values of y.

You only need the coordinates for two points, to be able to graph a line, so you only need to pick two values for x.

Since you're solving this system of linear equations by graphing, I suggest that you use graph paper.

I'll show you how to get coordinates for two points that lie on the line which is the graph of the following equation.

y = -2x + 5

Let x = 0

Substitute 0 for x in the formula for y, and do the math.

y = -2(0) + 5

y = 0 + 5

y = 5

Now we know that the y-coordinate is 5 when the x-coordinate is 0.

Plot the point (0, 5).

Now pick a second value for x. (It can be any value, but I will pick 5 so that the two points are not too close together.)

Let x = 5

Substitute 5 for x in the formula for y, and do the math.

y = -2(5) + 5

y = -10 + 5

y = -5

Now we know that the y-coordinate is -5 when the x-coordinate is 5.

Plot the point (5, -5)

Use a straightedge to draw a line through these two points.

Use the same method to determine the coordinates of two points on the other line (i.e., you pick two values for x and then find the corresponding values of y).

Draw a line through those two points, also.

The coordinates of the intersection point of these two lines give the (x,y) solution to the given system of two linear equations.

 
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