To solve a system of equations using substitution, we will start by isolating one of the variables in one of the equations. Then we can substitute whatever that variable equals into the other equation. Let's take a look an example.
y=2x+1 5x+2y=3 ⇒ y= 2x+1 5x+2( 2x+1)=3
If we happen to have a system of equations consisting of a vertical and horizontal line, we need to think about the general forms for these types of lines.
Vertical line: x=h, where h is any real number.
Horizontal line: y=k, where k is any real number.
Let's suppose that h=1 and k=2. Then we have the following system of equations.
x=1 y=2
There is no way to substitute the value of x or y into the other equation. Therefore, we cannot solve this system using substitution, and our friend is correct.
