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

my answer (x,y) = (-9,4)

textbook answer (x,y) = (9,-4)

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

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:

$\displaystyle 4x+3y=24$

$\displaystyle 4x-3y=0$

Can you finish?

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

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

Re: Few Questions on Systems of Linear Equations

Thanks. No wonder i keep making mistakes