# Few Questions on Systems of Linear Equations

• Nov 23rd 2012, 12:38 PM
Vince604
Few Questions on Systems of Linear Equations
I have a few questions on systems of linear equations. I tried them and either i get a negative answer that should be positive, or vice versa. I checked the answers on the back of the textbook and answers were different than mine. Please help.

Solve by elimination.
38=2x-5y
75=7x-3y

What i did to solve:
-7(38=2x-5y) 2((75=7x-3y)
-266=-14x+35y 150=14x-6y

150= 14x-6y
+(-266= -14x+35y)
-116 = 29y
-116/-29
y= 4

I use the same process to find x. x=-9

what did i do differently? where did i go wrong? help
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Solve by elimination:
x/3+y/4=2
2x/3-y/2=0

how do i break this down to solve?
i tried and ended up with y=2, text said x,y = 3,4
• Nov 23rd 2012, 12:50 PM
MarkFL
Re: Few Questions on Systems of Linear Equations
Where you have:

-116 = 29y
-116/-29 = y

You should have:

-116 = 29y
-116/29=y

Do you see why, and how this fixes your error?

For the second system, multiply the first equation by 12 and the second by 6 to get:

$4x+3y=24$

$4x-3y=0$

Can you finish?
• Nov 23rd 2012, 01:28 PM
Vince604
Re: Few Questions on Systems of Linear Equations
Quote:

Originally Posted by MarkFL2
Where you have:

-116 = 29y
-116/-29 = y

You should have:

-116 = 29y
-116/29=y

Do you see why, and how this fixes your error?

but when you bring the 29 over, why doesn't it change to -29? i dont understand
• Nov 23rd 2012, 03:21 PM
skeeter
Re: Few Questions on Systems of Linear Equations
if you subtract 29 from both sides, it becomes -29 ... you are dividing by 29, not subtracting
• Nov 23rd 2012, 07:22 PM
Vince604
Re: Few Questions on Systems of Linear Equations
Thanks. No wonder i keep making mistakes