MaTh = Algebra = help
posted by Rihanna on .
Solve this system of linear equaiton by an algebraic method.
So If I had to solve this the elimination method way, how would I do it?
x2y = 10
3xy = 0

x  2y = 10
3x  y = 0
eliminate y by multiplying 3x  y = 0 by 2
2(3x  y = 0) = 6x + 2y = 0
ADD the 2 equations
x  2y = 10
6x + 2y = 0
5x + 0 = 10
5x = 10
x = 2
substitute x = 2 in x  2y = 10, to find y
x  2y = 10
2  2y = 10
2y = 12
y = 6
check x = 2, y = 6
3x  y = 0
3(2)  6 = 0
6 + 6 = 0
0 = 0 
Oh so You have to multiply it by 2 because the first equation also uses 2 and you have to cancel them out that way right?
So if its  and + that means you have to add the equations. If its  and  that means you have to subtract and if it's + and + that also means you have to subtract right?
How did you get 2 as an answer?
Did you divide 5x by 5 and 10 by five to get 2?
You lost me right here:
How did you do this?
x  2y = 10
2  2y = 10
2y = 12
y = 6
How did you get the second line?
2  2y = 10?
And at the end you went 0 = 0
so they have to equal to zero always? 
How did you get 2 as an answer?
Did you divide 5x by 5 and 10 by five to get 2? YES
You lost me right here:
How did you do this?
x  2y = 10
2  2y = 10
2y = 12
y = 6
How did you get the second line?
2  2y = 10?
to find the value of y, since you know x = 2, you plug x = 2 into either equation and solve for y
the second line is from plugging 2 in for x in the equation x  2y = 10
x = 2
x  2y = 10
2  2y = 10
2y = 12
y = 6
yes, when you check, both sides will equal 0 if you are correct