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# AS maths C1 question watch

1. Q.Find the range of values of k for which the equation x^2-kx+(k+3)=0 has real roots.

So this means that b^2-4ac >= 0

But the answer in the book and solution book are both same which doesn't make sense. Can someone please solve this here so I can match my answer? Im pretty sure it's wrong in the book.
2. (Original post by Hamzah249)
Q.Find the range of values of k for which the equation x^2-kx+(k+3)=0 has real roots.

So this means that b^2-4ac >= 0

But the answer in the book and solution book are both same which doesn't make sense. Can someone please solve this here so I can match my answer? Im pretty sure it's wrong in the book.
Surely if two books agree on the answer then there isn't a problem?!

3. (Original post by davros)
Surely if two books agree on the answer then there isn't a problem?!

Book says the answer is -2<K<6

When my answer is K<=-2, K>=6

Thats why I want someone to solve it and see that the answer in the* book is totally wrong or maybe im missing something
4. k^2-4a(k+3)>0

Go from there.
5. (Original post by Vikingninja)
k^2-4a(k+3)>0

Go from there.
I did, thats how I got the final answer that a is 1 and I wrote >= looks like the book considered this as no real roots and took the equation as k^2-4(1)(k+3)<0
6. (Original post by Vikingninja)
k^2-4a(k+3)>0

Go from there.
I know it's not allowed in the rules to solve question here and just give hints but I have solved it and I need to compare with someone else can you solve it here?
7. (Original post by Hamzah249)
I did, thats how I got the final answer that a is 1 and I wrote >= looks like the book considered this as no real roots and took the equation as k^2-4(1)(k+3)<0
Could you post a picture of the question from the book please. Because I'm getting that -2 and 6 as k = 0 but the range between doesn't make sense.
8. (Original post by Vikingninja)
Could you post a picture of the question from the book please. Because I'm getting that -2 and 6 as k = 0 but the range between doesn't make sense.
https://gyazo.com/a5511ee5de7b49764c9675ac6ff37e0c
9. Ok yeah I'm getting the same answer as you on this question.
10. (Original post by Vikingninja)
Ok yeah I'm getting the same answer as you on this question.
Then it looks like the 2 books including step by step solution book are wrong on this one.
11. (Original post by serah.exe)
Here you go, excuse the paint skills lmao.
Attachment 461681
Oh well that makes sense.
12. (Original post by serah.exe)
Here you go, excuse the paint skills lmao.
Attachment 461681
That doesn't make any sense plot a graph and you will see that its k<-2 and K>6
13. (Original post by Vikingninja)
Oh well that makes sense.
14. (Original post by Hamzah249)
That doesn't make any sense plot a graph and you will see that its k<-2 and K>6
Yep, those workings do not make sense. Should be what you said.
15. (Original post by serah.exe)
Here you go, excuse the paint skills lmao.
Attachment 461681
16. (Original post by Illiberal Liberal)
It's squared.
17. Excuse my skills but aren't you suppose to be taking the part outside of the U shape graph https://gyazo.com/aa0690b2a656699353ee75f7007abcaa
18. Another dank quick graph example.

But the answer -2<K<6 should only appear if the graph was like this https://gyazo.com/aa14cd420634cfea8c55ef7272bb8020
19. k<-2
k>6

(My apologies to serah.exe )
Spoiler:
Show

I haven't done maths in a while
20. I just found the minimum point and it actually only works if it is equal to or smaller than -2 or greater than 6 so yeah im wtfing now. Should ask your teacher when you next see them.

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