# Inverses of Matrices

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## Objective

SWBAT find the inverse of a 2 x 2 matrix.

#### Big Idea

Students discover how to find the inverse of a matrix by analyzing the relationships between matrices and their inverses.

## Warmup

7 minutes

Today, I start class by giving students five minutes to complete the first two sections of the Mystical Matrices Worksheet. As they work, I say, "Pay particular attention to the arithmetic and the commonalities of each exercise." With about a minute remaining, I will ask students to use their graphing calculators to quickly multiply the last few matrices. I want them to do at least one by hand, but for this lesson the calculator will allow students to complete more examples and thereby have more results for comparison when we discuss.

Once time is up, we will work as a class to complete the missing information in the third section of the Worksheet. As we discuss their work, it is important for students to recognize the role of the zero and of the identity matrix in addition and subtraction of matrices.

40 minutes

## Closure

3 minutes

To close today's lessons on a positive note, I will ask my students to reflect on today’s learning by discussing the 3 W's Closure in their teams. I introduce the 3 W's on page 2 of Flipchart-Inverses of Matrices.