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C1 help!

The question is

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

I tried using the discriminant but didn't work.

Tablet battery is dying so I'll thank yous later!
Original post by techno-thriller
The question is

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

I tried using the discriminant but didn't work.

Tablet battery is dying so I'll thank yous later!


It does work :redface:

Since the roots are equal, the discriminant is equal to 0.

b2−4ac=0b^2 - 4ac = 0

⇒ 122−4(k)(k)=0\Rightarrow \ 12^2 - 4(k)(k) = 0

⇒ 144=4k2\Rightarrow \ 144 = 4k^2

kk is a positive constant so you must take the positive value when you find the square root of the equation of k2=...k^2 = ...
Original post by Khallil
It does work :redface:

Since the roots are equal, the discriminant is equal to 0.

b2−4ac=0b^2 - 4ac = 0

⇒ 122−4(k)(k)=0\Rightarrow \ 12^2 - 4(k)(k) = 0

⇒ 144=4k2\Rightarrow \ 144 = 4k^2

kk is a positive constant so you must take the positive value when you find the square root of the equation of k2=...k^2 = ...


DAMN!!! I forgot to square it! thanks:colondollar:
Original post by techno-thriller
DAMN!!! I forgot to square it! thanks:colondollar:


No prob :wink:

Now charge your tablet! :tongue:
Original post by Khallil
No prob :wink:

Now charge your tablet! :tongue:


Oh, it died when I was trying to edit my post to show my working for the discriminant:s-smilie::biggrin:

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