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# OCR MEI Maths - C1 - help

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1. How do i do 13 iii) - i don't get it :/
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2. write

x4 - 2 = kx2

investigate the Discriminant... this tells you how many roots the equation has.
3. (Original post by the bear)
write

x4 - 2 = kx2

investigate the Discriminant... this tells you how many roots the equation has.
Discriminant = b^2 - 4ac

....Stuck. What do i do with the x^4?
4. (Original post by tmifan)
Discriminant = b^2 - 4ac

....Stuck. What do i do with the x^4?
5. (Original post by the bear)
So its just:
(-k)^2 - (4 x 1 x -2)

= -k^2 + 8

Then?
6. (Original post by tmifan)
So its just:
(-k)^2 - (4 x 1 x -2)

= -k^2 + 8

Then?
discriminant = k2 + 8

what does that tell you ?
7. (Original post by tmifan)
So its just:
(-k)^2 - (4 x 1 x -2)

= -k^2 + 8

Then?
.
8. (Original post by the bear)
discriminant = k2 + 8

what does that tell you ?
...I don't know...
9. (Original post by tmifan)
...I don't know...
What does the discriminant always being greater than 0 mean?
10. (Original post by Zacken)
What does the discriminant always being greater than 0 mean?
2 roots!

but how do you know its greater than 0...from k2 + 8
11. (Original post by tmifan)
2 roots!

but how do you know its greater than 0...from k2 + 8
Well what do you know about a squared number? What do you get is you take a squared number and add a positive number?

If you cannot answer that, then think about what is (-100)^2 - what is (-200)^2 - what is (1)^2, what do they all have in common?
12. (Original post by Zacken)
Well what do you know about a squared number? What do you get is you take a squared number and add a positive number?

If you cannot answer that, then think about what is (-100)^2 - what is (-200)^2 - what is (1)^2, what do they all have in common?
Oh duhh! sorry that was a stupid question

Okay i get it now! Thank you both!

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