00:01
To solve this system of equations using the elimination method, we can start by adding both of these equations together.
00:09
If we do that, on the left -hand side, we're going to get x squared plus x is equal to negative 9.
00:22
Now what we're going to get over here is just, we're going to add 9 to both sides to get 9 on the other side, equals 0.
00:40
And it looks like here we're not going to be able to factor this normally because it's going to be hard to find.
00:47
A positive number that adds to just one x so we're going to have to use the quadratic formula which is just i'm going to list our a b and c values right here so it's easier later our a value is going to be one because there's nothing multiplied by the x squared b is also one because it's multiplied by just x which is just one and nine is going to be c now what i'm going to do is just write out our quadratic formula using what we have here.
01:24
So x is going to be equal to negative b, which is just 1, so negative 1 plus or minus b squared, which is just the square root of b squared, which is also just 1 minus 4 or ac.
01:49
A is still 1.
01:52
And now c is 9, all over 2a, which is still 1...