Question

Find the roots of the equation $x^2-1=0$ using quadratic formula.

• A. x = 1, 1
• B. x = 0, 1
• C. x = 0, -1
• D. x = 1, -1

Answer 1

The correct option is D x = 1, -1

Roots of the quadratic equation $a{x}^2+bx+c=0$ can be found out by using the quadratic formula, given by,
$x=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$.

Given, $x^2-1=0$
$x^2-1=0$ can be written as $x^2+0x-1=0$.
Then, a = 1, b = 0 and c = -1.
$\Rightarrow x=\frac{-0\pm \sqrt{0^2-(4\times 1\times -1)}}{2\times 1}=\frac{\pm \sqrt{4}}{2}=\pm 1$

Therefore, the roots of $x^2-1=0$ are $x=1$ and $x=-1$.