# Math 231

(Last updated Wednesday, Feb. 1 @ 4:45pm)## Course Information

Instructor: Professor Nicholas Vlamis

Instructor Office: 507 Kiely

Instructor Email: nicholas.vlamis@qc.cuny.edu

Class Meeting: Monday/Wednesday 10:05–11:55am in Kiely 242

Office Hour: Monday/Wednesday 4–5pm (or by appointment)

Textbook: Lay, David. Linear Algebra and Its Applications, Sixth Edition. Pearson, 2021.

## Week 2 (Week of January 30)

Helpful reading: Section 1.2 and 1.3.

Monday's Class: Introduced, discussed, and went over the augment martrix associated to a linear system, reduced row echelon form, and the Gauss–Jordan elimination algorithm.

Homework Assignment #1 (Due Wednesday, February 8)

No Quiz this week: first quiz will be next Wednesday.

The videos linked to on the right discuss how to find rref on a standard TI calculator and an example of someone going through the Gauss–Jordan elimination algorithm.

Wednesday's Class: Discussed how to solve a linear system using the reduced row echelon form of its associated augmented matrix. This involved introducing the notion of basic variables, free variables, and parameterized solutions. Part of our discussion was summed up in a theorem stating that a linear system is consistent if and only if the rightmost colum of the augmented matrix is

*not*a pivot column. And, moreover, a consistent linear system either has a unique solution (no free variable case) or infinitely many solutions (free variabls exist). We finished with introducing the notion of vectors, vector addition, and scalar multiplication.

## Week 1 (Week of January 23)

Helpful reading: Section 1.1 of text.

Wednesday's Class: Introduced Google's PageRank and worked through simple example. Defined linear system and worked through simple examples.

For those interested, the Google example was lifted from Strogatz's book

*The Joy of x*, which has nice examples of math in the real world.