Question

Solve the following system of equations algebraically:?
20x+Y=400
10x+y=600.....

Answer 1

Multiply the second equation by -2 and it will cancel out the x term.
Then you have:
20x + y = 400
-20x - 2y = -1200
This gives us the new set of equations:
-y = -800
y = 800
Plug in and solve for x.

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Answer 2

why do u Multiply it by -2?

Answer 3

where did u get the -2 from?

Answer 4

The way that this works is if we multiply an entire equation by a constant, it does not change the equation. Kind of like 1 is the same as 2/2 which is the same as 4/4.
Does this help?

Answer 5

This is what we call the elimination method.

Answer 6

well i'm still alittle lost.

Answer 7

help?

Answer 8

Sure. I have a video on youtube that explains the whole process. My youtube screen name is TutorSean. I don't have a video on it right now, but will soon.

Let me continue to try to clarify for you.

Answer 9

If we have two equations.
x + 2y = 1
x + 3y = 4

Then we can say leave equation 1 alone, and then multiply equation 2 by -1.
Then we have:
x + 2y = 1
-x - 3y = -4
If we rewrite the two equations together we have:
2y = 1
-3y = -4
Then we add together.
-y = -5
So y = 5

Then replacing y with negative 5 in either of the original equations gives us:
x + 2(5) = 1 which means that x + 10 = 1, x = -9

Do it in the second equation:
-x - 3(5) = -4
-x - 15 = -4
-x = 9
So x = -9

This shows that the system is what we call consistent. If you need some more help, please contact me through my webpage, http://www.tutorsean.net and I will be more than happy to help you through EMAIL or phone at no charge.
Sean