# Thread: How is it possible to find the Value of k?

1. ## How is it possible to find the Value of k?

Given:

kx^2 + 5x -3 = 0, and -3 is one of the roots.

i've been solving this using the sum and product of rryoots but it solving this does not fit the process.

i tried using quadratic formula, but still there is k.

Thank you so much.

2. ## Re: How is it possible to find the Value of k?

$x=\dfrac{-5\pm \sqrt{25+12k}}{2k}$

Try each (+ or -), setting it to -3 and solve for k.

3. ## Re: How is it possible to find the Value of k?

Originally Posted by rcs
Given: kx^2 + 5x -3 = 0, and -3 is one of the roots.
If $-3$ is a root, we know that $k(-3)^2+5(-3)-3=0$ so solve for $k$.

4. ## Re: How is it possible to find the Value of k?

hello :
- 3 is a root : k(-3)² +5(-3) -3 = 0
9k-18 = 0
9k=18
k=2