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bratzdoll3
Dec 17, 2006, 04:39 PM
what's the x coordinate of the solution of the following system od linear equations?
-3x-5y=-23
2x-4y=-14

is the answer

a. 4
b. 0
c. -4
d. -1
e. 1

how do you do this?

Capuchin
Dec 17, 2006, 04:51 PM
for simultaneous equations, you need to multiply up so you can get rid of a variable.

In this case you want X, so we need to get rid of y

If you multiply all terms in your top equation by 4 and all terms in your bottom equation by 5, you will have 2 equations both with -20y in them.

You can then subtract the two equations, ending up with 0y and an amount of x, it's then simple algebra to solve for x.

Let me know how you get on!

CaptainForest
Dec 17, 2006, 10:11 PM
If I have done my math correct…..

-3x-5y=-23
2x-4y=-14

-5y=-23 + 3x
-4y =-14 – 2x

y = 4.6 - 0.6x
y =3.5 + 0.5x

3.5 + 0.5x = 4.6 - 0.6x
0.6x + 0.5x = 4.6 – 3.5
1.1x = 1.1
x = 1

Capuchin
Dec 18, 2006, 05:27 AM
Ewww dividing.

Multiplying up is your friend.

CaptainForest
Dec 19, 2006, 12:31 AM
-5y=-23 + 3x
x4
= -20y = -92 + 12x


-4y =-14 – 2x
X 5
= -20y = -70 – 10x


-92 + 12x = -70 – 10x
12 x + 10 x = -70 + 92
22x = 22
x = 1

I still get x=1

Capuchin
Dec 19, 2006, 06:10 AM
Well yes... I'm not saying you're wrong :p

CaptainForest
Dec 19, 2006, 12:53 PM
Lol