# Thread: make y the subject 4x+3y+15

1. ## make y the subject 4x+3y+15

this question has stumped me so can u plz help thanx :

make y the subject 4x+3y+15

2. ## Make the subject

Doesn't that just mean to solve for y?
$4x+3y+15=0$
$3y=-(4x +15)$
$y=\frac{-(4x +15)}{3}$

3. ## (4,y) (2,7) solve for y

thanx man i got a bit stuck on another one
(4,y) (2,7)
you have to solve for y again by using the (x1 y1) (x2 y2) method and where m=y2-y1 over x2-x1 < thats a fraction hopefully u can help thanx

4. You need to learn to write your problems out correctly. In your first post you wrote "make y the subject 4x+3y+15" which makes no sense- that is an expression, not an equation and has no "subject". Gamma assumed you mean 4x+ 3y+ 15= 0. If that was what you meant, you are lucky!

Now you write "(4,y) (2,7)" and say "you have to solve for y again..." I think you mean that (4,y) and (2,7) are points some line must pass through. The slope of such a line would be $\frac{y- 7}{4-2}= \frac{y- 7}{2}$ but unless you are given the slope to set that equal to, I see no equation to solve for y.

5. Yeah dude that was a shot in the dark. Same for this one, all I can hope is you mean.

$m=\frac{7-y}{2-4}=\frac{7-y}{-2}=-\frac{7}{2}+\frac{y}{2}$

Thus $m+\frac{7}{2}=\frac{y}{2}$

$y=2m+7$