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# Algebra II Terms

## Get down with the lingo

### Cramer's Rule

A matrix-style method for solving square systems of equations. We bust out a coefficient matrix, track down the determinant D, and swap out each variable column for a constant column to get the new determinants Dx and Dy. To solve for x, divide Dx by D. To solve for y, divide Dy by D. It's got more letters than a Chekhov play, but it's super useful.

### Determinant

While it sounds like the name of some cheesy product from an "As Seen On TV" infomercial, it's actually a special number derived from a square matrix. It's useful to know sometimes, and it's written as |A| = adbc for a 2 × 2 matrix.

### Entries

Each number or variable inside the brackets of a matrix.

### Identity Matrix

The matrix version of the number 1, i.e. the best matrix. At least, it thinks that it's #1. More objectively speaking, it's a square matrix with a line of 1s running diagonal from upper-left to lower-right, with the rest of its entries as 0s.

### Matrix

Variables or constants arranged like a grid in rows and columns that together make up a rectangle. The rows go across, and the columns are vertical; they're like the columns in the Lincoln Memorial. Here's a 2 × 2 matrix:

### Scalar

A constant multiplied throughout a matrix. That doesn't sound exciting, until everything in your matrix is suddenly a thousand times bigger. Hope you packed something good in there!

### Square Matrix

A matrix that has the same number of rows and columns. Literally, square matrices look square.

### Zero Matrix

The matrix version of the number 0, i.e. a matrix filled with 0s. It can be any size, but try and be reasonable about it.