Thread: Quadratic Functions exam paper question

Given that the equation

kx^2 - 4x + k - 3 = 0

has equal roots, find the value of "k".

I know that a=k, b=-4, and c=k-3.

Then to put it into b^2 - 4ac I'd get:

(-4)^2 - 4 (k) (k-3) = 0
16 - 4k^2 + 12k = 0
[I can cancel down to:] 4 - k^2 + 3k = 0

But I'm not sure what to do from here can someone please help

Originally Posted by db5vry

Given that the equation

kx^2 - 4x + k - 3 = 0

has equal roots, find the value of "k".

I know that a=k, b=-4, and c=k-3.

Then to put it into b^2 - 4ac I'd get:

(-4)^2 - 4 (k) (k-3) = 0
16 - 4k^2 + 12k = 0
[I can cancel down to:] 4 - k^2 + 3k = 0

But I'm not sure what to do from here can someone please help

Now you have to solve 4 - k^2 + 3k = 0 => k^2 - 3k - 4 = 0.

keep going, solve last equation: k^2-3k-4=0 (k-4)(k+1)=0, k=4;-1