Question

If one root of the quadratic equation $x^2-11x+k=0$ is $9$, then find the value of $k$.

Answer 1

Given quadratic equation is $x^2-11x+k=0$

One root is $9$

Putting $x=9$ in the given equation,

$x^2-11x+k=0$

$\Rightarrow (9{)}^2-11(9)+k=0$

$\Rightarrow 81-99+k=0$

$\Rightarrow -18+k=0$

$\therefore k=18$.