Question

discriminant:
COMPUTE THE DISCRIMINANT: (d =b^2 -4ac)

for the equation: (-1/6x^2) +3x -9 = 0

Answer 1

9-4(-1/6)(-9)=9-36/6=9-6=3

Answer 2

how do you solve can i get the steps :)

Answer 3

eitaK:

Check out the following:
http://answers.yahoo.com/question/index?qid=20080304153003AAUaVrd

Answer 4

Hey eitaK, I would multiply all terms by -6 to get:
\[x ^{2}-18x+54=0\]
then the discriminant would be \[-18^{2}-(4)(1)(54)=324-216=108\]

Answer 5

so technically you are getting rid of the fraction in the first step right?

Answer 6

and then how did you do the next step?

Answer 7

Yesm I believe twhitelsu is also correct. I am sort of confused here.

Answer 8

The next step was to square b (-18*-18) then subtract the 4ac or subtract (4*1*54)

The results did not equal the same as twhitelsu, and there is nothing wrong with the way it was done to get 3

Answer 9

ok but what happened to the x's?

Answer 10

I would stick the a, b, c, values of the original equation

Answer 11

ok so that is what i didn't and i go t -18^2- 4(1)(54)

Answer 12

sorry d= -18 not t.

Answer 13

The discriminant only deals with the coefficients of the variable not the variable itself. So there are no x in the discriminant.

Answer 14

ok

Answer 15

so then i went further and got-18^2 = -324 and then -4(1)(54) = -216

Answer 16

so then i woudl have D= -324 -216 correct?

Answer 17

Yes, but it doesn't come out as 3, as you would get if you had used the original equation for the values of a, b, c. I thought multiplying thru would simplify it, but it came out with a different discriminant. So apparently multipllying thru by-6 was not the right thing to do. I will think some more about this. I think you are on to the procedure to obtain discriminants.

Answer 18

i just used the equation that i was given. that i put abvoe :/

Answer 19

I just noticed that if I divides the results of 108 by 6 squared (36) it would be 3!!.

Answer 20

wait but where did you get 108

Answer 21

you've lost me,

Answer 22

The discriminant is that part of the quadratic formula that is within the radical and it is used to the following way: If it is greater than 0, their are two real solutions. If it equals zero there is one real solution (repeated).
If it is less than 0, there are no real solutions.

Answer 23

The -18 squared results in positive 324 (not the -324) when then combined with the -216 you get the 108 which is positive and means there are 2 real solutions.

Answer 24

ok... because it it positive?

Answer 25

and greater than 0 correct?

Answer 26

Yes

Answer 27

ok so then how do i get three as the discriminant?

Answer 28

Look at the work at the top of this page provided by twhitelsu.

Answer 29

She worked the probllem using the original equation working with the fractional value for a.

Answer 30

if i am going of yours, which makes a little more sense to me... how did you think and know to do that?

Answer 31

Did you follow her steps, see where b (3) was squared to become a 9

Answer 32

no i don't see where she got the 4 from.

Answer 33

I was trying to get rid of the 1/6 (I don't like fractions) lol the result were still positive but was not equal

Answer 34

i mean looking at hers. i see she has 4

Answer 35

the 4 was given in the discriminant equation: b^2-4ac, it is part of the 4ac. get it

Answer 36

you can see where she uses the a and c values being that a = -1/6 and c=-9

Answer 37

oh yes haha thanks.

Answer 38

but isn't the b supposed to be squared ? so 9^2

Answer 39

Look at your equation (-1/6)x^2+3x-9=0 the abc values for your equation are:
a=-1/6, b=3, c=-9 So b=3 and b squared if 9

Answer 40

gotcha! wow haha

Answer 41

THANKS FOR SPENDING ALL THAT TIME ON THIS PROB!

Answer 42

Here is form for a quadratic equation:

\[ax ^{2}+bx+c=0\]
Note that the abc represents numbers with a and b being the coefficients of variables and c is a constant.

Answer 43

wait whats that for?

Answer 44

oh i see.