Question

Find roots of equation $x^2-11x+28=0$ by quadratic formula

• A. $4,7$
• B. $-4,-7$
• C. $4,-7$
• D. $-4,7$

Answer 1

The correct option is A $4,7$

$x^2-11x+28=0$

We have a formula for solving quadratic equation $a{x}^2+bx+c=0$ is

$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$

$x=\frac{11\pm \sqrt{121-112}}{2}$

$x=\frac{11\pm \sqrt{9}}{2}$

$x=\frac{11\pm 3}{2}$

$x=\frac{11-3}{2};x=\frac{11+3}{2}$

$x=\frac{8}{2};x=\frac{14}{2}$

$x=4,7$