## a few different formulas for linear functions

Simplificatation, evaluation, linear equations, linear graphs, linear inequalities, basic word problems, etc.
santaclaus
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Joined: Tue Mar 03, 2009 12:17 am
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### a few different formulas for linear functions

1. If they say, Slope -4, x-intercept 7,
does this mean that y=-4x+7?????

2. Slope 3, y-intercept 8, does this mean y=3x+8?

3. Passes through the points (-1,5) and (2,-1)
would it be possible for me to state y=3x-6?

4. Slope 2/3 and passes through the point (5, 7)
does this mean y=2/3x +7?

5. Has x-intercept 3 and y-intercept -5
does this mean y=3x-5?

6. Slope 0.1, passes through (-0.1, 0.02)
does this mean y=0.1x+0.02?

7.Function f has f(0.3)=0.8 and f(0.8)=-0.4
I have no idea what this means -

8. Function f has f(-2)=7 and f(3)=-3
what does this mean? do I have to input -2 as a value of x? and -3 as a value of x? how do I get my y values and how do I create a formula for this linear function.

I'm starting to understand, but need to be a little more confident -- really appreciate all you've done -- Elizabeth is your name? I need to send you chocolates or something -- thanks again for all your help on all the problems that you've taken the time to help me out with!!!!!!!!!!1

stapel_eliz
Posts: 1628
Joined: Mon Dec 08, 2008 4:22 pm
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### Re: a few different formulas for linear functions

1. If they say, Slope -4, x-intercept 7,
does this mean that y=-4x+7?
The equation "y = -4x + 7" does represent the straight line with slope m = -4, but it has a y-intercept of 7, not an x-intercept of 7.

. . . . .Straight-Line Equations
. . . . .Graphing with Slope and y-Intercept
. . . . .Slope of a Straight Line
. . . . .Intercepts
2. Slope 3, y-intercept 8, does this mean y=3x+8?
The equation "y = 3x + 8" does have a slope of m = 3 and a y-intercept at y = 8. If the question (not included within the post) was "state the equation with the following properties", then your equation is correct.
3. Passes through the points (-1,5) and (2,-1)
would it be possible for me to state y=3x-6?
How did you arrive at this equation? Please show all of your steps.
4. Slope 2/3 and passes through the point (5, 7)
does this mean y=2/3x +7?
How did you arrive at this equation? (For instance, since the line is clearly not horizontal, and since the line clearly passes through y = 7 at x = 5, not at x = 0, how did you arrive at a y-intercept of 7?) Please show all of your steps.
5. Has x-intercept 3 and y-intercept -5
does this mean y=3x-5?
Since the points (3, 0) and (0, -5) do not result in a slope of m = 3, how did you arrive at your equation? Please show all of your steps.
6. Slope 0.1, passes through (-0.1, 0.02)
does this mean y=0.1x+0.02?
I have the same question here as for (4) above...?
7.Function f has f(0.3)=0.8 and f(0.8)=-0.4
I have no idea what this means -
Your class certainly does seem to skip a lot...

To learn about functions and function notation, try here:

. . . . .Functions
. . . . .Function Notation

Once you have learned what their notation means, you'll see that they've given you two points, (x, y) = (0.3, 0.8) and (x, y) = (0.8, -0.4). Then you can proceed as usual.
8. Function f has f(-2)=7 and f(3)=-3
what does this mean? do I have to input -2 as a value of x? and -3 as a value of x? how do I get my y values and how do I create a formula for this linear function.
Study the lessons in the links for exercise (7) to learn the necessary background material.

santaclaus
Posts: 41
Joined: Tue Mar 03, 2009 12:17 am
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### Re: a few different formulas for linear functions

so basically, if they want you to find an equation going through points given, whether its 1 or 2 points, I must first find the b or y-intercept and then plug any of the points back into the equation? also assuming I've found the slope? y-y1/x-x1?

stapel_eliz
Posts: 1628
Joined: Mon Dec 08, 2008 4:22 pm
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so basically, if they want you to find an equation going through points given, whether its 1 or 2 points, I must first find the b or y-intercept and then plug any of the points back into the equation?
No. The y-intercept is what you find once you've created the line equation, and then solved it for "y=".

Try reading the lesson on straight-line equations. It's got loads of examples of how to work these things out.