# Help with y=mx+c

• Apr 21st 2012, 09:49 PM
jabelone
[SOLVED] Help with y=mx+c
Hello,
I have come across this problem and need help solving it. Give the equation of the line from (3, -3) to (-1, 3) in the y=mx+c format. (Headbang)
• Apr 21st 2012, 10:20 PM
biffboy
Re: Help with y=mx+c
m is the gradient of the line. So m= (3 minus -3) divided by (-1 minus 3) When you have found m put it into y=mx+c. Now substitute into this x=3 and y=-3 (because you know this point fits the line) and you will get c.
• Apr 21st 2012, 10:30 PM
jabelone
Re: Help with y=mx+c
thanks,
So would this be right: y = -1.5 x 3 + 3

Thank-you for your help, I couldn't find it in my notebook.
• Apr 21st 2012, 11:47 PM
biffboy
Re: Help with y=mx+c
You are correct that m= -1.5 So equation is y= -1.5x + c Now (3,-3) is on this line so -3= (-1.5*3)+c which gives c=1.5

So equation of line is y= -1.5x+1.5
• Apr 22nd 2012, 12:18 AM
jabelone
Re: Help with y=mx+c
Thank you very much.
• Apr 22nd 2012, 05:22 AM
Wilmer
Re: Help with y=mx+c
Another way.
Once you get the slope of -3/2, you need to find c in (0,c).
Use one of given poinrs; say (3,-3):
(-3 - c) / (3 - 0) = -3/2
-6 - 2c = -9
c = 3/2