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# C1!!! Question watch

1. Given that the equation kx^2+12x+k=0, where k is a positive constant, has equal roots, find the value of k.

(4 marks)

Any useful hints? I prefer them to actual solutions! (but feel free)

Cheers
2. discriminant = 0 for equal roots
3. this thread is a duplicate... so i'm sorry to say that it's been answered already...
4. k, i gotta question relating to this. suppose u got x^2 + bx + c = 0, and the roots of the are (1 + sqrt 5) and (1 - sqrt 5)
how would u go about answering this? like wat do u have to do, an explanation will do just fine.
thanx

edit: sorry didn't write out teh complete question, yeah so u have to find out the value of b and c!
5. roots are:
[-b ± sqrt[b² - 4ac] ] / 2a
so as roots are 1±sqrt5
then
1±sqrt5 = [-b ± sqrt[b² - 4ac] ] / 2a
a is 1 ( as it's x²)
so:
1±sqrt5 = [-b ± sqrt[b² - 4c] ] / 2
so 1 = -b/2
b = -2

and 1/2 sqrt [ b² - 4c] = sqrt 5
sqrt[b²/4 - 4/4 c] = sqrt 5
sqrt[(-2)²/4 - 4/4 c] = sqrt 5
sqrt[1 - c] = sqrt 5
so:
1-c = 5
c = -4
6. (Original post by Lawbutwhere?)
Given that the equation kx^2+12x+k=0, where k is a positive constant, has equal roots, find the value of k.

(4 marks)

Any useful hints? I prefer them to actual solutions! (but feel free)

Cheers

Equal roots mean that the discriminant = 0

b^2 - 4ac is the discriminant. I will give you no more clues, hope this helps.
7. lol...

this thread is a duplicate... so i'm sorry to say that it's been answered already...
no need to give more clues!

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