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Curve Sketching Urgent Help Please !??!?

Please can someone give me a step by step to solving this. I have no clue what this question is. I have several more like this and I'm doing them for my own benefit to improve. So if you could use the following question as an example so I can learn from it to do all the others. I will greatly appreciate any help and thanks in advance to anyone who does.

Question:

Show that the equation x^2 + (k-2)x -4 = 0 has real and distinct roots for all values of K
Original post by Aty100
Please can someone give me a step by step to solving this. I have no clue what this question is. I have several more like this and I'm doing them for my own benefit to improve. So if you could use the following question as an example so I can learn from it to do all the others. I will greatly appreciate any help and thanks in advance to anyone who does.

Question:

Show that the equation x^2 + (k-2)x -4 = 0 has real and distinct roots for all values of K


Do you know what the discriminant is?
(edited 8 years ago)
Original post by Aty100
Please can someone give me a step by step to solving this. I have no clue what this question is. I have several more like this and I'm doing them for my own benefit to improve. So if you could use the following question as an example so I can learn from it to do all the others. I will greatly appreciate any help and thanks in advance to anyone who does.

Question:

Show that the equation x^2 + (k-2)x -4 = 0 has real and distinct roots for all values of K


Have you learnt about the discriminant? What happens when b24ac>0 b^2-4ac > 0?

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Reply 3
Original post by Princepieman
Have you learnt about the discriminant? What happens when b24ac>0 b^2-4ac > 0?

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There are two real solutions?
Original post by Aty100
There are two real solutions?


Cool so what happens when you sub in the coefficients of the quadratic equation?
Reply 5
Original post by Princepieman
Cool so what happens when you sub in the coefficients of the quadratic equation?


Not sure what I'm doing :/ :frown:
You need to use the discriminant (as described above).

When the discriminant > 0, there are 2 distinct, real solutions.
When it = 0, you get a repeated root
When it < 0, you get no real roots at all (you get imaginary roots instead but you don't have to worry about them... for now...)

Discriminant.png

Regardless of the value of k, the discriminant k^2 - 4k + 20 is always going to be greater than 0. So, we can conclude that there are two real roots.

Here's a link: http://regentsprep.org/regents/math/algtrig/ate3/discriminant.htm

Hope this helps :smile:
(edited 8 years ago)
Original post by PeterTheHe
You need to use the discriminant (as described above).

When the discriminant > 0, there are 2 distinct, real solutions.
When it = 0, you get a repeated root
When it < 0, you get no real roots at all (you get imaginary roots instead but you don't have to worry about them... for now...)

Discriminant.png

Regardless of the value of k, the discriminant k^2 - 4k + 20 is always going to be greater than 0. So, we can conclude that there are two real roots.

Here's a link: http://regentsprep.org/regents/math/algtrig/ate3/discriminant.htm

Hope this helps :smile:


Bro, it'd help if you allowed them to get to the solution themselves rather than just give it to them.
Reply 8
Original post by PeterTheHe
You need to use the discriminant (as described above).

When the discriminant > 0, there are 2 distinct, real solutions.
When it = 0, you get a repeated root
When it < 0, you get no real roots at all (you get imaginary roots instead but you don't have to worry about them... for now...)

Discriminant.png

Regardless of the value of k, the discriminant k^2 - 4k + 20 is always going to be greater than 0. So, we can conclude that there are two real roots.

Here's a link: http://regentsprep.org/regents/math/algtrig/ate3/discriminant.htm

Hope this helps :smile:


Yah thanks, but I managed to realise I substituted it into the wrong formulas straight after posting so got the same answer :smile:
Reply 9
Original post by PeterTheHe
You need to use the discriminant (as described above).

...

Hope this helps :smile:


Please don't post full solutions - it's against forum guidelines :smile:

If you stick to hints and suggestions then the OP should be able to make progress by himself.
Original post by Aty100
Please can someone give me a step by step to solving this. I have no clue what this question is. I have several more like this and I'm doing them for my own benefit to improve. So if you could use the following question as an example so I can learn from it to do all the others. I will greatly appreciate any help and thanks in advance to anyone who does.

Question:

Show that the equation x^2 + (k-2)x -4 = 0 has real and distinct roots for all values of K


This is related to the discriminant. As it says the equation has 'real and distinct' roots, it means that it will have two different roots. By looking at the equation, it is apparent that it's a quadratic equation. So, the form of it is ax^2 + bx + c = 0. In this case, a = 1, b = k-2 and c = -4

For the equation to have two real and distinct solutions or roots, the discriminant (b^2 - 4ac) will have to be greater than (>) 0.

So, you have to show the discriminant is greater than 0 by substituting the values of a, b and c into the discriminant.


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Original post by Chittesh14
This is related to the discriminant. As it says the equation has 'real and distinct' roots, it means that it will have two different roots. By looking at the equation, it is apparent that it's a quadratic equation. So, the form of it is ax^2 + bx + c = 0. In this case, a = 1, b = k-2 and c = -4

For the equation to have two real and distinct solutions or roots, the discriminant (b^2 - 4ac) will have to be greater than (>) 0.

So, you have to show the discriminant is greater than 0 by substituting the values of a, b and c into the discriminant.


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You're only a few hours late...

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Original post by Princepieman
You're only a few hours late...

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Lol but this is proper guidance towards how to answer the question without answering the question.
I felt like writing it :smile:


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