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Math Question

post #1 of 14
Thread Starter 
I have a math question. Right before the winter break we started working on solving formulas/equations for a specified variable. Here are some examples so far (answers in parenthesis):
d=rt, solve for t
(d/r=t)

3x + 4y= 12, solve for y
(y= -3x + 12/4)

f=v + at, solve for t
(t= f - v/a)

This is what I'm not sure how to do:
2x - 3y + 7, solve for y

The other problems have an equal sign. I can't find anything in my text book about this. Is it possible to solve for "y" without there being an equal sign?
post #2 of 14
maybe the minus sign should have been an equal
post #3 of 14
IIRC, when there's not an equal sign there you just add " = 0 " to the end of it and work it like you would the others... but math is the one thing I have absolutely no memory for, so I'm likely wrong.
post #4 of 14
2x - 3y + 7, solve for y

10=y + 2

I am not too sure on this.....just my guess and my hubby's
post #5 of 14
Quote:
Originally Posted by strange_wings View Post
IIRC, when there's not an equal sign there you just add " = 0 " to the end of it and work it like you would the others... but math is the one thing I have absolutely no memory for, so I'm likely wrong.
She's right; can't be done unless you add = 0 to the end of the equation.

(I recognize that first one, LOL, distance = rate * time)
post #6 of 14
Thread Starter 
Quote:
Originally Posted by kluchetta View Post
She's right; can't be done unless you add = 0 to the end of the equation.

(I recognize that first one, LOL, distance = rate * time)
So I have to add = 0 to the expression to make it an equation before I can solve it?
post #7 of 14
I THINK it's not an "equation" without an equal sign...
post #8 of 14
Thread Starter 
Quote:
Originally Posted by kluchetta View Post
I THINK it's not an "equation" without an equal sign...

You're right, it's not an equation without the "=" sign.

I found the problem in my book but it's written as an equation:
2x - 3y = 7

The answer to this would be:
y= 2x - 7 / 3

I emailed my instructor about it and asked if there was a typo on the handout since the problems were coming from review sections we haven't covered in the text book. Makes for good practice.
post #9 of 14
Thread Starter 
Figured it out:
2x - 3y + 7

2x - 3y + 7 = 0

y= 2x + 7 / 3
post #10 of 14
Quote:
Originally Posted by Essayons89 View Post
Figured it out:
2x - 3y + 7

2x - 3y + 7 = 0

y= 2x + 7 / 3
You know, math really isn't supposed to have missing pieces! It really can drive you crazy when that happens.
post #11 of 14
Thread Starter 
Quote:
Originally Posted by kluchetta View Post
You know, math really isn't supposed to have missing pieces! It really can drive you crazy when that happens.
You got that right!
post #12 of 14
Quote:
Originally Posted by Essayons89 View Post
Figured it out:
2x - 3y + 7

2x - 3y + 7 = 0

y= 2x + 7 / 3
When I saw this, I thought that you were figuring out a slope on a line with x and y coordinates and that is why you would be solving for 0.

Confirmed this with enginenerd DH:

As he described it, "It is a line on a graph in the Cartesian plane. X = horizontal, y = vertical, the slope of the line is 2 and the x-intercept, (where y= 0) is at - 7/6.

Hey, at least I knew it was a graph and we were solving for x and y coordinates. I did take calculus and got a B+ in differential and and A+ in integral - go figure. I actually liked calculus but now I do financial systems math where debits must equal credits and the only line is the profit line.
post #13 of 14
Quote:
Originally Posted by strange_wings View Post
IIRC, when there's not an equal sign there you just add " = 0 " to the end of it and work it like you would the others... but math is the one thing I have absolutely no memory for, so I'm likely wrong.
Exactly right.

Quote:
Originally Posted by Essayons89 View Post
You're right, it's not an equation without the "=" sign.

I found the problem in my book but it's written as an equation:
2x - 3y = 7

The answer to this would be:
y= 2x - 7 / 3

I emailed my instructor about it and asked if there was a typo on the handout since the problems were coming from review sections we haven't covered in the text book. Makes for good practice.


Figured it out:
2x - 3y + 7

2x - 3y + 7 = 0

y= 2x + 7 / 3


I think your missing something though. First you want to get y on a side by itself. Then when you divide by 3 you divide the entire thing by 3. I moved the 3y to the right to keep it positive, otherwise you would divide by -3 instead of 3.
2x-3y=7
2x-7=3y
(2x-7)/3=y

OR

2x-3y+7=0
2x+7=3y
(2x+7)/3=y

The only difference here if 2x-7 or 2X+7
post #14 of 14
Quote:
Originally Posted by butzie View Post
...I did take calculus and got a B+ in differential and and A+ in integral - go figure...
Go figure?
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