# Find an Equation for a Line?

• Mar 8th 2010, 08:57 PM
EandH
Find an Equation for a Line?
Hi. I need help finding the slope intercept equation for this point and slope. Here is what I have so far:

Find the slope intercept equation for the line with the indicated slope and y-intercept.
Slope 5/7 ; y-intercept (0,4)
Y = 5/7x+b
4 = 5/7 (0)+ b
4 = 5/7 + b
5(0)/7 + b =4
• Mar 8th 2010, 09:36 PM
Bacterius
Well ... basically if you have the slope $\displaystyle m$ and the y-intercept $\displaystyle c$ (or the point $\displaystyle (0, c)$) then the equation of the line is simply $\displaystyle y = mx + c$.

If you have the slope and one point that is not the y-intercept, then you need to use the coordinates of the point to solve $\displaystyle y = mx + c$ for $\displaystyle c$, with $\displaystyle (x, y)$ the coordinates of the points ($\displaystyle m$ is known as you have the slope)
• Mar 8th 2010, 09:57 PM
EandH
Thank you, but I'm still not sure I understand
• Mar 8th 2010, 10:02 PM
Bacterius
Quote:

Originally Posted by EandH
Thank you, but I'm still not sure I understand

What don't you understand ?
• Mar 8th 2010, 11:54 PM
jgv115
Easy:

take $\displaystyle y=mx+c$

Where m is the gradient or the slope
and c is the y intercept.

So you've given us the slope which is $\displaystyle \frac{5}{7}$ and the y intercept is the y point where x=0.

The co-ordinates you have given us is (0,4)... x is 0 in this so the y intercept is 4.

Substitute:

$\displaystyle y=\frac{5}{7} x +4$
• Mar 9th 2010, 12:28 AM
Bacterius
Quote:

Originally Posted by jgv115
Easy:

take $\displaystyle y=mx+c$

Where m is the gradient or the slope
and c is the y intercept.

So you've given us the slope which is $\displaystyle \frac{5}{7}$ and the y intercept is the y point where x=0.

The co-ordinates you have given us is (0,4)... x is 0 in this so the y intercept is 4.

Substitute:

$\displaystyle y=\frac{5}{7} x +4$

Thank you for completing 100% of his question, that will surely help him ... please people, don't answer someone's question entirely (except if it is really an awesome question), but instead give him hints or tips or a direction to follow ... otherwise he just reads brainlessly and it's not as useful :(

That being said, maybe that some people *need* to be answered the whole question as an example that they can follow, so I won't go on about this.
____________

By the way, you were right in your reasoning EandH, your equation was correct and the fraction actually cancels out due to the zero, leaving $\displaystyle b = 4$ (called $\displaystyle c$ in both of our posts) which is correct.
• Mar 9th 2010, 11:05 AM
EandH
thanks
Okay, I see now. Thank you all very much. I didn't understand how to put together what I was doing so I appreciate the explaination.