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1. Not sure if this is step level or below Its just one of the prep questions I am meant to do before my step class and I cant figure it out.

question 16
find the real values of K for which the equation x^2+ (k+1) +k^2=0 has
A real roots, B, one root is double the other.

part A is is easy that is just using the discriminant and then drawing a graph and stating the values of the inequalities of X.

K is => -1/3 or K is =<1

I successfully got that part rather quickly but I cant figure out how to proceed to do part B

I mean I know that in terms of roots A+B= -b/a and since a is 1 A+B=-b

I get that. I also get that root A * root B = c/a which again since a is 1 just gives K2

but I don't know where to go from here.

I mean I tried putting this into a quadratic inbetween inequalities which got messy and nowhere.

I mean having -1/3<=(-(k+1)+-root(-3k^2+2k+1))<= 1 does not seem like I am doing this right might have made a mistake somewhere too but I have a strong feeling this is not the right method.

Help
2. oh and I am aware that if A+B= -b and one root is twice the other then A+2A= -b would give 3a= -b

but have not managed to find a way of using that.
3. (Original post by Luke7456)
..
If the roots are R and 2R, then the sum of the roots is 3R and the product of the roots is 2R^2. This is enough to find k.

Also, don't post maths problems in this forum, as the sticky says:

(Original post by DFranklin)
This University Mathematics forum is for discussion of mathematics that is specifically to do with studying at university.

That is, for questions like "Do you think I would enjoy a Maths degree", or "Should I apply to Warwick or Imperial?", or "Is it possible to change to maths from physics after one year?".

It is not for questions like "How do you integrate exp(-x^2)?". The correct forum for those questions is the Maths Forum that is part of the "Study Help" set of forums.
4. (Original post by Luke7456)
Not sure if this is step level or below Its just one of the prep questions I am meant to do before my step class and I cant figure it out.

question 16
find the real values of K for which the equation x^2+ (k+1) +k^2=0 has
A real roots, B, one root is double the other.

part A is is easy that is just using the discriminant and then drawing a graph and stating the values of the inequalities of X.

K is => -1/3 or K is =<1

I successfully got that part rather quickly but I cant figure out how to proceed to do part B

I mean I know that in terms of roots A+B= -b/a and since a is 1 A+B=-b

I get that. I also get that root A * root B = c/a which again since a is 1 just gives K2

but I don't know where to go from here.

I mean I tried putting this into a quadratic inbetween inequalities which got messy and nowhere.

I mean having -1/3<=(-(k+1)+-root(-3k^2+2k+1))<= 1 does not seem like I am doing this right might have made a mistake somewhere too but I have a strong feeling this is not the right method.

Help

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