Question

If one root of the quadratic equation $x^2-7x+k=0$ is $3$, then find the value of $k$.

Answer 1

Given, one root of the quadratic equation $x^2-7x+k=0$ is $3$
$\therefore$ Substituting $x=3$ in the given equation
$x^2-7x+k=0$
${\left(3\right)}^2-7\left(3\right)+k=0$
$\therefore$ $9-21+k=0$
$\therefore$ $9-21+k=0$
$\therefore$ $-12+k=0$
$\therefore$ $k=12$