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How do you solve simultaneous equations using the substitution method ?x=y ...
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So these are two separate simultaneous equations, right? And x actually equals y in the first one?
If so, in the first one, just substitute y for x. Then you will have 6y - 2y = 10. That becomes 4y = 10 and that becomes y = 2.5.
The other one is a little more complicated since x = -y, but it's the same process. You substitute -y for x. Then you will have
-3y - 6y = 36
That gets you
-9y = 36
And y = -4
Since x = -y, x = -(-4). Two negatives make a positive and x = 4
Posted by pohnpei397 on March 17, 2010 at 1:53 PM (Answer #1)
I am assuming that we are talking about 2 different systems since x=y in the first and x=-y in the second.
For the first system where x = y, simply substitute x for y. Then 6x - 2y becomes 6x -2x. So 6x -2x = 4x =10. Divide both sides by 4 and you have x = 2.5 => y = 2.5.
For the second system:
Since x = -y, then replace x with -y. Then 3x - 6y becomes 3(-y) - 6y. Now, we have -3y - 6y = -3y + -6y = -9y =36. Divide both sides by -9 and we have y= - 4 => -y = 4 => x = 4.
If you need to solve each with x=y and x=-y, then you would follow the same steps for the other equation. In other words, use x = -y for substituting in 6x - 2y. Then you would have 6(-y) - 2y = -6y - 2y = -8y = 10. Divide both sides by -8 and get y = -1.25. Since x= -y, the x = 1.25.
Posted by job518 on March 17, 2010 at 2:10 PM (Answer #2)
Simultaneous equations are solved by substituting one variable for the other and setting the equation equal to 0, or if it has a constant. This is simply done by exchanging one for the other, for example, x=y, 6x-2y=10. You have to substitute y for x and the equation becomes:
The other equations for y, substituting x for y is the same process.
It is a very easy and straightforward process for you to solve similar equations using the same process.
Posted by epollock on March 17, 2010 at 2:40 PM (Answer #3)
High School Teacher
There are two pairs pair of equations, each pair having two variables x and y.
are simultaneous linear equations in two variables x and y.
Since x=y , substitute y = x in (ii) and we get: 6x-2x = 10. Or 4x = 10 . Therefore, x = 10/4 = 2.5. Since y = x, y = 2.5
x=-y ..................(1) and
Though it is easy to substitute x= -y, we go different. From the second equation (dividing both sides by 3) we get x-2y = 12 . Or x = 12+2y. Substituting this x in terms of y in (1), we get:
12+2y = -y Or Subtracting 2y from both sides, we get:
12 = -3y Or y = 12/-3 = -4. So x =-y = -(-4) = 4.
Posted by neela on March 17, 2010 at 3:51 PM (Answer #4)
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