Question

Solve the following quadratic equation by using the formula method: $m^2-3m-10=0$

Answer 1

$m^2-3m-10=0$
Comparing with $a{x}^2+bx+c=0$
$a=1,b=-3,c=-10$
$m=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$
$=\frac{3\pm \sqrt{(-3{)}^2-4(1\left)\right(-10)}}{2\times 1}$
$=\frac{3\pm \sqrt{9+40}}{2}=\frac{3\pm \sqrt{49}}{2}=\frac{3\pm 7}{2}$
$\therefore m=\frac{3+7}{2}$ and $\frac{3-7}{2}$
$\therefore m=\frac{10}{2}$ and $\frac{-4}{2}$
$\therefore m=5$ and $-2$.