Question

if x=3 is one root of quadratic equation x^2-2kx-6 then find value of k

Answer 1

we know that 3 is one factor hence take x = 3

substituting values we get

9 - 6k - 6 = 0
3 - 6k = 0
3 = 6k
hence k = 1/2 

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Answer 2

x² -2 kx - 6

If x = 3 is one of the roots

⇒ the quadratic will return us the value zero when we substitute x = 3 into the equation.

Substitute x = 3 and equate the equation to 0:

(3)² -2k(3) - 6 = 0

9 - 6k - 6 = 0

3 - 6k = 0

6k = 3

k = 1/2

Answer: The value of k is 1/2