WEBVTT

1
00:00:00.000 --> 00:00:07.210
Here is the problem: negative 4x plus 3y equals 2; 6x plus y equals 30.

2
00:00:07.660 --> 00:00:10.737
2 linear equations in 2 unknowns (x, y).

3
00:00:11.537 --> 00:00:17.621
Write every equation in standard form. Move all variable terms to the left and constants to the right.

4
00:00:18.071 --> 00:00:22.204
Build the augmented matrix [A | b]. Columns: x, y | constant.

5
00:00:22.654 --> 00:00:29.051
Gauss–Jordan elimination. Use row operations to make each pivot 1 and clear the rest of its column.

6
00:00:29.501 --> 00:00:31.927
Divide R1 by negative 4.

7
00:00:32.728 --> 00:00:35.480
Clear column 1 using the pivot in R1.

8
00:00:35.930 --> 00:00:38.519
Divide R2 by 11 over 2.

9
00:00:38.969 --> 00:00:41.744
Clear column 2 using the pivot in R2.

10
00:00:42.194 --> 00:00:44.040
Reduced row-echelon form.

11
00:00:44.840 --> 00:00:46.558
Read off the unique solution.

12
00:00:47.358 --> 00:00:51.236
So the answer is x equals 4, y equals 6.

13
00:00:51.686 --> 00:00:57.282
The system has exactly one solution; substituting it back satisfies every equation.

14
00:00:58.082 --> 00:01:03.666
Equation 1: negative 4x plus 3y equals 2, which checks out.

15
00:01:04.116 --> 00:01:09.224
Equation 2: 6x plus y equals 30, which checks out.
