Question

Choose the value of the coefficient determinant (D) in the following system.

2x – 5y = –2
x – 3y = 0

Answer 1

The coefficient matrix is made up of the coefficients of x and y: \[\left[\begin{matrix}a & b \\ c & d\end{matrix}\right] = \left[\begin{matrix}2 & -5 \\ 1 & -3\end{matrix}\right]\]
The determinant of that is found by multiplying the diagonal terms and subtracting them in the form of ad-bc: \[\left| \left[\begin{matrix}2 & -5 \\ 1 & -3\end{matrix}\right] \right| = 2(-3)-(-5)(1)=-6+5=-1\]

Answer 2

Choose the value of the x determinant (Dx) in the following system.

3x – 4y = –7
x + y = 7

Answer 3

their is an x?? instead of just an an x

Answer 4

d i mean

Answer 5

Hmm I am not sure what is meant by "x determinant." I don't believe I've heard that term before. However here is a link to a question similar to yours, perhaps the answer there can help you: http://answers.yahoo.com/question/index?qid=20101219091339AAmbZLk

Answer 6

What are the choices of values you are supposed to choose from?

Answer 7

21 28 -14 -35

Answer 8

Ok if you use the method the person used in that link I posted, you will get a number that is included in those choices you listed.

Answer 9

its 35! :[)?

Answer 10

Well that is not what I got. Show me what you did.

Answer 11

[3.4]
[1.1]
4-3=1
-7.4
7.1
28+7=35??

Answer 12

Your answer is a little confusing. Why are you doing 4-3=1?
Note: your "D" coefficient matrix needs to have a -4, not 4.

Answer 13

so the answer is -35?

Answer 14

No, how would you get -35? Plug in the -4 in and see what you get when you do the math.
\[\left[\begin{matrix}-7 & -4 \\ 7 & 1\end{matrix}\right] = ?\]

Answer 15

(-7)(1)-(-4)(7)=-7+28 = ...?

Answer 16

ohhhhhh....thats how i got 35..i got the negatives mixed up..

Answer 17

its 21 ok..

Answer 18

Yep, just had to have a -4 instead of a 4. If the method that person in the link posted is correct, then your answer should be correct.

Answer 19

may you do one more?

Answer 20

Choose the value of the y determinant (Dy) in the following system.

2x – 4y = 24
2x – 3y = 15
–132
–12
–18
78

Answer 21

Well now that you have done one, you should be able to do another one, using that same method. I assume now that it's y instead of x though, you use the x column (2,2) instead of the y column like in the previous problem.

Answer 22

well can you atleast check my answer :3?

Answer 23

Sure.

Answer 24

-12?

Answer 25

Well, you get -12 if you use the y coefficients (-4,-3) like in the previous problem, which asked you for the x determinant, so I assume that -12 is your x determinant. If you want the y determinant, I assume you have to use the x coefficients then (2,2)... but that gives me an answer of 18, not -18 like in your choices. So I am uncertain here -- hopefully someone else can pick it up.

Answer 26

it was 18..... thank you and goodnight

Answer 27

Oh okay. You are welcome. Good night :)