00:01
So in this problem, we have x minus y is equal to negative 1.
00:06
Now we also have x squared minus y is equal to negative 4.
00:14
Okay, so working with this equation, it wants us to solve by using substitution.
00:20
So i'm going to use this first equation and just solve for x.
00:24
So just add y to both sides.
00:26
So x is equal to y minus 1.
00:32
Now we're going to use that expression and plug it into our second equation.
00:35
So we're going to have this x expression squared minus y is equal to negative 4.
00:44
We're plugging in y minus 1.
00:47
So we'll need to do a quick binomial expansion to the power of 2.
00:52
So to do that, we just do we square the first term.
00:57
We multiply 2 by each term.
01:00
So 2 times y times negative 1 is negative 2 y.
01:05
Then negative 1 squared is just plus 1 and then subtract y to get negative 4.
01:18
Okay, so this simplifies down a little bit...