Question

The zeros of the equation $x^2+8x+9=0$, can be

• A. $x=-1\pm \sqrt{7}$
• B. $x=-2\pm \sqrt{7}$
• C. $x=4\pm \sqrt{7}$
• D. $x=-4\pm \sqrt{7}$

Answer 1

Answer: (D)

$x=-4\pm \sqrt{7}$

Given equation is

$x^2+8x+9=0$

By using quadratic formula,

$a=1,b=8,c=9$
$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$

$x=\frac{-8\pm \sqrt{64-4\left(1\right)\left(9\right)}}{2\times 1}$

$x=\frac{-8\pm \sqrt{28}}{2}$

$x=\frac{-8\pm 2\sqrt{7}}{2}$

$\therefore x=-4\pm \sqrt{7}$

$\therefore$ Zeros of the given equation are $-4\pm \sqrt{7}$

Hence, option D.