00:02
Already, let's say we have the system of equations, 2x plus y equals negative 2 and 3x minus y equals 7.
00:08
And i want to solve this by substitution.
00:17
In this method, i want to substitute one equation and for the other.
00:21
So one of the things i need to do is step number one is isolate a variable.
00:27
So i'm going to choose to isolate this y here because there's no coefficient in front of this.
00:34
So why did i isolate this variable in this equation? instead of the y in the second equation.
00:41
And it has to do with the positive sign because that's a positive 1y instead of a negative 1y.
00:48
If i were to isolate this y here, i would have to divide by negative 1.
00:54
I'm looking for the least amount of work possible.
00:58
So i have 2x plus y equals negative 2.
01:05
I'm going to subtract 2x from both sides...