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Math guys (1 Viewer)

skol asylum

skol asylum

Footballguy
Pre-calc problem for my 16 year old...

Problem wants an equation of a line that passes thru the intercept of one equation and is parallel to the line of another equation. Assuming on the second part you need to find the same slope as second equation. Equation is given as 2x + 3y -1. Confusing as this is not in a line equation format. Y=mx+b

Wondering if this is a typo or if there is a way to graph a line using that? Been too many years and they seem to be going beyond my basic algebra skills.

Anyone? TIA!

 
cap'n grunge said:
Equation is given as 2x + 3y -1. Confusing as this is not in a line equation format. Y=mx+b
Click to expand...
Isn't your equation missing an equals sign?  You need to perform the same operations on both sides to isolate the y and get it into the right format.

So if it's 2x + 3y -1 = 0, then 2x + 3y = 1, 3y = 1 - 2x, y = 1/3 -2/3x.

 
Yeah, the first equation I left out because that one is used for the y intercept. The second one which I gave is supposed to be used to calc the slope. No equal sign given.

 
Dr_Zaius said:
Isn't your equation missing an equals sign?  You need to perform the same operations on both sides to isolate the y and get it into the right format.

So if it's 2x + 3y -1 = 0, then 2x + 3y = 1, 3y = 1 - 2x, y = 1/3 -2/3x.
Click to expand...
That's what I was wondering, if you're supposed to assume it equals zero but I don't think you can assume that. 

 
cap'n grunge said:
That's what I was wondering, if you're supposed to assume it equals zero but I don't think you can assume that. 
Click to expand...
No, you definitely can't assume that.  You're correct that there's a typo.  Most likely it's supposed to be one of 2x + 3y -1 = 0, 2x +3y = 1, or 2x +3y = -1.  Those are all just guesses though - it's unsolvable without an equals sign somewhere.

 
Dr_Zaius said:
Isn't your equation missing an equals sign?  You need to perform the same operations on both sides to isolate the y and get it into the right format.

So if it's 2x + 3y -1 = 0, then 2x + 3y = 1, 3y = 1 - 2x, y = 1/3 -2/3x.
Click to expand...
This. It's unsolvable in its current form.

 
Navin Johnson said:
If it is parallel to 2x + 3y = 1, then it will be 2x + 3y = n.  Plug in your intercept value to figure out what n is.
Click to expand...
This post did get me thinking, though, that all three of the equations listed below have a slope of -2/3 as they are all parallel to each other.

Dr_Zaius said:
No, you definitely can't assume that.  You're correct that there's a typo.  Most likely it's supposed to be one of 2x + 3y -1 = 0, 2x +3y = 1, or 2x +3y = -1.  Those are all just guesses though - it's unsolvable without an equals sign somewhere.
Click to expand...
Initial problem is definitely wrong/underdefined, but you can probably back out the correct answer with that logic.  The only way it'll end up being wrong is if the equation is actually supposed to be 2x = 3y -1, as then the sign of the slope would be different.

 
Dr_Zaius said:
This post did get me thinking, though, that all three of the equations listed below have a slope of -2/3 as they are all parallel to each other.
Click to expand...
You don't need y = mx + b to replicate slope.  You just need to rewrite the equation you are taking slope from with the same x and y coefficients and calculate the new constant.  Can be done in standard form as well as slope-intercept, yet most kids think they have to know what the actual slope is and take the unnecessary step of converting it into slope-intercept.

 
Navin Johnson said:
You don't need y = mx + b to replicate slope.  You just need to rewrite the equation you are taking slope from with the same x and y coefficients and calculate the new constant.  Can be done in standard form as well as slope-intercept, yet most kids think they have to know what the actual slope is and take the unnecessary step of converting it into slope-intercept.
Click to expand...
Yes, I agree with this and it is a good point.  However, I think the original reason for the confusion in this case is not standard form vs. slope-intercept, but the fact that technically there is no equation given in the problem.  We are making educated guesses as to what the equation actually is.  

 
Full problem...

Write the equation of a line in slope-intercept form that passes through the y intercept of y=2x^2 + 1 (2x squared) and is parallel to the line 2x + 3y - 1.

 
cap'n grunge said:
Full problem...

Write the equation of a line in slope-intercept form that passes through the y intercept of y=2x^2 + 1 (2x squared) and is parallel to the line 2x + 3y - 1.
Click to expand...
So they figured out the first part with a y intercept of +1. Parallel line to what probably is a typo would have the same slope.

 
I googled 2x+3y-1 and every response from the search was for 2x+3y=-1. So its got to be an error cause you know, google is never wrong. 

 
Dr_Zaius said:
Yes, I agree with this and it is a good point.  However, I think the original reason for the confusion in this case is not standard form vs. slope-intercept, but the fact that technically there is no equation given in the problem.  We are making educated guesses as to what the equation actually is.  
Click to expand...
This guy's got upper management written all over him. Great communicator.

 
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