Question

Solve for x if det = 24

| 2 x |
|5 -3 |

Answer 1

Do know this rule: \[\det\left[\begin{matrix}a & b \\c & d\end{matrix}\right]=ad-bc?\]

Answer 2

i've seen it before

Answer 3

Ok so what we do is \[\det\left[\begin{matrix}2 & x \\ 5 & -3\end{matrix}\right]=2(-3)-(x)(5)=-6-5x\]

But the problem tells us that \[\det \left[\begin{matrix}2 & x \\ 5 & -3\end{matrix}\right]=24\]

Answer 4

Can you see what we can do next?

Answer 5

i think we multiply the det??? not sure

Answer 6

No it's much easier than that. We have that the det is equal to -6-5x and equal to 24

Answer 7

Thus you just need to solve -6-5x = 24, by simple algebra :)

Answer 8

oh so we add 6 to both sides then divide by 5

Answer 9

yes, and then just multiply by (-1) since you'll have -x=___

Answer 10

-x=6
but dont we have to remove the -x which will turn it into x=-6

Answer 11

yes, it's essentially the same operation :)

Answer 12

thanks do you mind helping me with another

Answer 13

np. sure

Answer 14

Use the determinant to find the area of the triangle with the following vertices:
(-3,1)
(1,-3)
(2,3)
(remember area is positive, do not add units squared as the computer will count it incorrect.)

Answer 15

I'm not sure why you need determinants. You can just use basic geometry to find the area of a triangle

Answer 16

I've never used determinants to find the area of a triangle, but there is great info here: http://people.richland.edu/james/lecture/m116/matrices/applications.html

Answer 17

ive tried that site but i dont know where to gt my det from

Answer 18

@goformit100 help me please

Answer 19

hey @goformit100 do you know how to do the second question

Answer 20

@ganeshie8

Answer 21

that site given by @kirbykirby explains the method. see if you can understand it... its bit tedious to explain :( you can come back and ask if u don't get something... give it a try :)

Answer 22

but where does the det come from

Answer 23

These are the vertices of triangle :-

(-3,1)
(1,-3)
(2,3)

Answer 24

you need to fill them for 1st and 2nd columns

Answer 25

last column you fill wid 1's

Answer 26

-3 1 1
1 -3 1
2 3 1

Answer 27

find the determinant of this matrix

Answer 28

???

Answer 29

how to find the determinant of a 3x3 matrix: http://www.youtube.com/watch?feature=player_embedded&v=21LWuY8i6Hw#at=271

Answer 30

det=-50

Answer 31

@ganeshie8 is that right

Answer 32

@GoldPhenoix i need some help
|2 7 -3|
|-1 5 -4|
|6 9 0 |

Answer 33

I don't know how to do matrices. Sorry.

Answer 34

kk

Answer 35

@Jhannybean please help

Answer 36

using the given. matrices find the value of its determinant:
|2 7 -3|
|-1 5 -4|
|6 9 0 |

Answer 37

New problem?

Answer 38

no same one just put the hole problem up

Answer 39

Just follow the steps in the video stated by @kirbykirby . You'll be able to solve this :)

Answer 40

okay thanks