Question

How do you find the value of `k` given that one solution of the equation `x^2-kx+21=0` is `3`?

Answer 1

`k=10`

Explanation:

`x=3` is one solution.

Putting `x=3` in the equation `x^2-kx+21= 0`

we get `3^2-k*3 +21=0 or 3k =30 or k=10`

`k=10` [Ans]