Calculating Inverse Matrices 93

That's t

bad...

Actually...we also

could have solved

−1

a

11

a

21

a

12

a

22

with...

...this formula

right here.

Huh?

Let's aly

the formula

to our

previous

example:

3

1

1

2

We got

the same

answer as

last time.

Why even bother with

the other method?

Ah, we...

This formula only works

on 2×2 matrices.

If you want to find

the inverse of a

bier matrix, I'm

afraid you're going

to have to sele for

Gauian elimination.

H

94 Chapter 4 More Matrices

Next, I thought

I'd show you how

to determine

whether a matrix

has an inverse

ornot.

So...some matrices

lack an inverse?

−1

3

1

6

2

Let's

s...

Oh, the

denominator

becomes zero.

I gue you're

right.

One last thing:

theinverse of an

invertible matrix

is, of course,

alsoinvertible.

Makes

sense!

Invertible

Not

invertible

Yeah. Try to calculate the

inverse of this one with the

formula I just showed you.

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