Help, once again! Solving Equations for Y

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ok, this time a diffrent subject.....

stuff like 2x-y=5, and -3x+4y=8

I was sick when she tuaght the lesson, and i wasnt able to get her help with it, or get notes. so, im lost...... and i have twenty of those to do!
 
ok: solve Each Equation for Y, show all work. thats all the directions i got

?
 
ArmyBrat said:
ok, this time a diffrent subject.....

stuff like 2x-y=5, and -3x+4y=8

I was sick when she tuaght the lesson, and i wasnt able to get her help with it, or get notes. so, im lost...... and i have twenty of those to do!
Click to expand...

Let's take the first one.
. . .
\(\displaystyle 2x-y=5\)
. . .
What you are trying to do is get y by itself on one side. So, what we do first is subtract 2x from both sides to rid the left side of the 2x.
. . .
\(\displaystyle -y=-5x+5\)
. . .
Now, you have y as a negative number. You need it to be positive, so divide each side by -1. (Because -y is the same as (-1)(y).)
. . .
\(\displaystyle y=\frac{-5x+5}{-1}\)
. . .
\(\displaystyle y=5x-5\)
. . .
Now, that's y=mx+b form. You have y by itself on one side, then you have that equal to m(the slope of the line) times x plus your b (which is the y-intercept of the equation). This is the easiest form of an equation to graph a line with. Yes, there are other ways, but this is the easiest. If you need more help, just let me know!
. . .
I'd like to see if you can try to work out the second one that you posted. :) I know you can do it!
 
ok for the 2x-y=5 one, this is what you do. you have to get it in the slope-intercept form. y=mx + b. or y= m(x) + b .. same thing.

2x - y = 5
-2x = -2x subtract 2x from each side
-y = -2x + 5 after this, since you have the opposite of y, switch it
y = 2x -5

your slope (m) = 2
and your y-intercept = 5

hope that helps.. dont really know what you're looking for.

the second problem, -3x + 4y = 8

-3x + 4y = 8
+3x = +3x add 3x since its already negative to eliminate it from the left side
4y = 3x + 8
4 4 divide each side by 4 to isolate y
y = 3/4x + 8/4 simplify
y = 3/4x + 2

slope (m) = 3/4
y-intercept = 2
 
Ahhh! Sorry, I accidentally switched it over to a 5 instead of a 2...Eep! Sorry.
 
ArmyBrat said:
ok, this time a diffrent subject.....
stuff like 2x-y=5, and -3x+4y=8
I was sick when she tuaght the lesson, and i wasnt able to get her help with it, or get notes. so, im lost...... and i have twenty of those to do!
Click to expand...
Why get in slope and intercept? All that's asked is solve for y.

2x-y=5 : y = 2x - 5 [1]
-3x+4y=8 [2]

Subs [1] in [2]:
-3x + 4(2x - 5) = 8 ..... carry on
 
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