-x + 5y = 3 eq1
x - 5y = -3 eq2
We want to find the value of x and y that will satisfy both equations. There are two ways we can do this.
1) Substitute one equation into another
2) Use elimination method by multiplying the equations by a certain number, and then adding or subtracting the equations to eliminate either the x terms or y terms.
These methods both allow us to get to one equation with one variable, since it is difficult to solve an equation that has two different variables. I intend to show you both.
Substitution method:
From eq2,
x = 5y - 3
Substitute this value of x into eq1. This will allow us to have eq1 in terms of y only and we only have one equation to work with.
-(5y - 3) + 5y = 3
-5y + 3 + 5y = 3
Notice that -5y and 5y cancel each other out. The equation now becomes 3 = 3.
We could not solve for y, but the end result turned out to be true.
Elimination method:
If we add the equations together, we obtain
0x + 0y = 0
We could not solve for either x nor y, but the equation is true. 0 times x is 0. 0 times y is 0. 0 + 0 = 0. This is true also.
Now, I would like to show you a visual method. The graphical method. We graph these equations on the same coordinate system. First, we need to write each of the given equations in slope-intercept form.
Eq1
5y = x + 3 ---> y = (1/5)x + 3/5
Eq2
-5y = -x - 3 ---> y = (1/5)x + 3/5
Notice that these equations are the same line. This means that the solution is infinite. The other methods mentioned above also show this.
David W.
y is a "function" of x. That means, that for each x, there is a unique y.
line - you know, straight line. It can be represented
in standard form as Ax + By = 0
or in slope-intercept form as y = Mx + B
solve - means to find the point(s) where the lines intersect.
For lots of lines, this is true. But, parallel lines never intersect and the same line ... (see answer)
We usually represent the answer as a point, for example: (3.4)
05/28/15