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Solve the following equestion?? Quadratics... watch

1. Solve the following equation, give irration answers in terms of surds.

x^4 - 5x^2 + 4 = 0

therefore

t^2 - 5t + 4 = 0

Factorised as

(t - 1)(t - 4)

Therefore

t = 1 or 4

x = t^2 so

x = 1 or 16.. WRONG

so now i try putting t^2 - 5t + 4 = 0 into the quadratic formula

again, t is 1 OR 4

...

The answer in the book is saying +/- 1 OR +/- 2 ???

Thanks,
Sean
2. t doesn't equal x^2
x^2 equals t

(hope this helps )
3. or

You have squared. This is not the right thing to do to find x!

Edit: I said t and meant x!

4. So

5. (Original post by Mr M)
or

You have squared. This is not the right thing to do to find t!
what is right then?
6. (Original post by loopylouise)
t doesn't equal x^2
x^2 equals t

(hope this helps )
I know what you are trying to say but you haven't managed it!
7. (Original post by Bleak Lemming)
what is right then?
What operation "reverses" squaring?
8. (Original post by Mr M)
I know what you are trying to say but you haven't managed it!
...rats... ah well, other people said it better... I'm gonna get some cafine
9. (Original post by StephenP91)

So

Is there anything you would like to change about that last line?
10. (Original post by Mr M)
Is there anything you would like to change about that last line?
Besides plus or minus, but I have taken that as a given. That and I can't remember how to do it in LaTex.
11. (Original post by StephenP91)
Besides plus or minus, but I have taken that as a given.
Why have you taken that as given?
12. (Original post by Mr M)
Why have you taken that as given?
Look what I have said. I could have just typed it, but writing on this stupid IPod is effort as it is.
13. oh just give him the answer. He'll learn better when he realizes what simple mistakes he has done:

(x^2 - 1)(x^2 - 4)

x^2 = 1, 4.
x = root(1 and root(4 = +/- 1 and +/- 2
14. (Original post by StephenP91)
Look what I have said.
Ah-ha.

/pm in latex
15. When solving equations of the form (where k is positive), about one quarter of AS students only find the positive solution.

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Updated: April 13, 2011
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