1. Feb 11, 2014

Matejxx1

1.given the equation a(3x2+2x+1)=4x-6x2-4 with the solutions x1 and x2
a) let a=0 without solving the equation calculate x1-3+x2-3

the correct answer is supposed to be -7/2

2. Relevant equations
x1+x2=-b/a
x1*x2=c/a

3. The attempt at a solution
The first thing I was that I put in "a" so,
0*(3x2+2x+1)=4x-6x2-4
0=4x-6x2-4................... here I multiplied the whole equation by -1
0=6x2-4x+4...........................here i divided the equation by 6
0=x2-4/6x+46
then I used the equation
1/x13+1/x23=(1/x1+1/x2)3 -3/x12x2 -3/x22x1
This is where I have no idea how to continue.I'm not even sure that what I have written is correct .If someone could help me solve this,I would really appreciate it. Thanks for reading .

2. Feb 11, 2014

ehild

Try to bring in x1+x2 and x1x2.
For example, $$1/x_1+1/x_2=\frac{x_1+x_2}{x_1 x_2}$$

ehild

3. Feb 11, 2014

Matejxx1

thank you for your reply. I did as you said and I got:
((x1+x2)/x1x2)3-3x1/x12x22 -3x2/x22x12. then I added the minuses together:
((x1+x2)/x1x2)3-3x1+3x2/(x1x2)2
Did I do this part correct?
May I also ask, what command did you use to write (x1+x2)/x1x2 because your way looks much easier to understand

Last edited: Feb 11, 2014
4. Feb 11, 2014

Ray Vickson

He did not write $x_1+x_2/x_1x_2$; you did that. In fact, you wrote
$$x_1 + \frac{x_2}{x_1 x_2}$$
If you mean
$$\frac{x_1 + x_2}{x_1 x_2}$$
then either use LaTeX or else use parentheses, like this: (x1+x2)/x1x2.

5. Feb 11, 2014

Matejxx1

Thank you I didn't notice that and I fixed it right away

6. Feb 11, 2014

Matejxx1

Now I added in the numbers
x1+x2=4/6
x1*x2=4/6
(((4/6)/4/6))-((3*4/6)/(4/6)2 =
1-(2)/0,444=
1-4,5=-3,5=-7/2
Thank you very much for your help I got the right answer

7. Feb 11, 2014