00:01
Okay, if i want to solve this system of equations by substitution, by using the substitution method, i want to substitute one of the equations into the other.
00:14
So what i need to do is i need to isolate a variable.
00:18
And so i always like to look for a variable that doesn't have a coefficient in front of it, such as this x.
00:24
You can isolate whatever variable you want to, but depending on when you choose, depends on how much work you're going to have.
00:31
So if i have the equation x minus 2y equals negative 5 and i want to isolate the x, i would add 2y to that sides.
00:45
And that would give me x equals negative 5 plus 2y.
00:52
So now i can take this negative 5 plus 2y and i can substitute it in for x in the second equation there.
01:03
So if i rewrite that second equation, instead of writing 2x, i would write 2 times negative 5 plus 2y minus 3y equals negative 4.
01:25
Ready? so let me distribute that 2.
01:28
So that's going to be negative 10 plus 4y minus 3y equals negative 4...