1. ## Algebra and Surds!

Find the exact value of

x² + 1/x²

if x = 1 + 2 * square root of 3 / 1 - 2 * square root of 3

2. Does anyone end up with this answer?? Pls help! I dnt kno whether it's a printing error in the textbook or I just cnt solve it

3. Originally Posted by Mirage
Does anyone end up with this answer?? Pls help! I dnt kno whether it's a printing error in the textbook or I just cnt solve it

I don't know how to arrive at that answer. Would you be able to type out your working out pls?

5. Would be more helpful if you used some brackets, is this the question? find $\displaystyle \frac{x^2+1}{x^2}$ where $\displaystyle x = \frac{1+2\sqrt{3}}{1-2\sqrt{3}}$

6. It is x² + (1/x²)
second part is correct

Sorry, I'm new to this. How do you type maths? Is there some sort of program that you use?

7. Originally Posted by Mirage

Sorry, I'm new to this. How do you type maths? Is there some sort of program that you use?
Have a quick read of this. http://www.mathhelpforum.com/math-he...orial-266.html

8. Originally Posted by Mirage
It is x² + (1/x²)
$\displaystyle (\frac{1+2\sqrt{3}}{1-2\sqrt{3}})^2+\frac{1}{(\frac{1+2\sqrt{3}}{1-2\sqrt{3}})^2}$

Start expanding brackets.

9. You also can find x+1/x=2cos(t) (much easier )

and then x^2+(1/x^2)=2cos(2t)

10. Originally Posted by Also sprach Zarathustra
You also can find x+1/x=2cos(t) (much easier )

and then x^2+(1/x^2)=2cos(2t)
Good advice ASZ, although remember this is in a pre-uni level forum.