Question

Determinants and Inverses Quiz Help! question and image attached

Answer 1

I need to show my work. So i want to understand it, I dont just want answers

Answer 2

for addition (and substraction) to work, both matrices must have the same dimension.

Answer 3

what does that mean?

Answer 4

A is 2 by 2, but B is 2 by 3. so addition and substraction are not defined (cannot be performed)

Answer 5

oh i see. Can you help with another ?

Answer 6

Wrong

Answer 7

Objection in the court

Answer 8

what x.x

Answer 9

if u multiply both matrices and get the identity matrix, then they r inverses.

Answer 10

No he is wrong

Answer 11

Think about it

Answer 12

So #1 is wrong? The answer is definitely "not possible" i just need to know why

Answer 13

NOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO LISTEN TO WHAT IM SAYING

Answer 14

The entire thing is wrong

Answer 15

-_- i dont understand what youre trying to say though

Answer 16

Read my lipsss

Answer 17

no. look at the screenshot. the quiz has already been graded. the answer is "not possible". im making corrections but i need to explain why the answer is what it is

Answer 18

OMG Read my lips

Answer 19

you make no sense. im listening to @helder_edwin

Answer 20

I'll just explain

Answer 21

Don't be so rude

Answer 22

It makes me cry at niight

Answer 23

@BAZINGA153760 you are not being neither helpful nor making any sense.

Answer 24

Laying down the laws

Answer 25

Okay think about it!

Answer 26

Again for addition (and subtraction) to be defined both matrices must have the same dimension.

in the exercise, since A is 2 by 2 and B is 2 by 3, u CANNOT subtract them.

Answer 27

Wrong

Answer 28

hes right. i just refered to my textbook

Answer 29

@helder_edwin LISTEN TO WHAT IM TELLING YOU

Answer 30

I know more

Answer 31

Prove it, let me see this text book!

Answer 32

There is no way

Answer 33

youre not telling us anything but to listen to what youre telling us....im blocking you

Answer 34

listen to what im saying

Answer 35

regarding the second problem if u multiply both matrices and get the identity matrix, then by definition the matrices are inverses.

Answer 36

right. what about this one?

Answer 37

two matrices r equal if the corresponding entries are equal so:
\[\large -12=2k \qquad 2f=-14 \]
\[\large -w^2=-81\qquad 3=3 \]

Answer 38

WRONG

Answer 39

LISTEN TO WHAT IM SAYNG

Answer 40

so k=-6
f=-7

Answer 41

@bazinga153760: your comments are totally inappropriate and out of place here. You are spamming, and, worse, you are interrupting a problem solving session begun by others.

Answer 42

yes, u r right.
u forgot to solve for "w".

Answer 43

i know. i cant figure it out x.x

Answer 44

well u have
\[\large -w^2=-81 \]
from which
\[\large w^2=81 \]
so
\[\large w=9\qquad\text{or}\qquad w=-9 \]

Answer 45

\[ but -9^{2} doesnt equal -81...\]

Answer 46

yes it does:
\[\large -w^2=-(-9)^2=-81 \]

Answer 47

don't forget that
\[\large -w^2\neq(-w)^2 \]

Answer 48

ahh. i see i see

Answer 49

last one

Answer 50

do u want the answer or the procedure?

Answer 51

i guess the procedure is a lot more helpful. i will use the definition of a determinant using cofactors.

Answer 52

\[\large \begin{vmatrix}
-4 & 5 & 6\\ 0 & 4 & 4\\ -2 & -5 & 4
\end{vmatrix}=
(-4)\begin{vmatrix}
4 & 4\\ -5 & 4
\end{vmatrix}+(5)(-1)\begin{vmatrix}
0 & 4\\ -2 & 4
\end{vmatrix}
+(6)\begin{vmatrix}
0 & 4\\ -2 & -5
\end{vmatrix} \]

Answer 53

Excuse my interrupting, but I'd thought that this quiz was to be on determinants and inverses. None of the conversation up to now has focused on determinants, only on operations with matrices. Only now are you beginning to focus on a problem involving the inverse of a 2x2 matrix. Are you both sure that you're spending time on what is most important to @yelahn?

Answer 54

You don't need to answer ME...just be clear about where you're spending your time and energy and why. Good luck.

Answer 55

im pretty sure it all applies. the quiz is titled Determinants and Inverses.

Answer 56

\[\large =(-4)[4\times4-4\times(-5)]-(5)[0\times4-4\times(-2)]+6
[0\times(-5)-4\times(-2)] \]
\[\large =(-4)(16+20)-(5)(0+8)+(6)(0+8) \]
\[\large =(-4)(36)-(5)(8)+(6)(8) \]
\[\large =-144-40+48=-136 \]

Answer 57

i just did the work for that problem. it matches yours. so hopefully it is correct @helder_edwin

Answer 58

great!