Find the Discriminant x^2-4x-5=0

$x^{2} - 4 x - 5 = 0$

Step 1

The discriminant of a quadratic is the expression inside the radical of the quadratic formula.

$b^{2} - 4 (a c)$

Step 2

Substitute in the values of $a$ , $b$ , and $c$ .

${(- 4)}^{2} - 4 (1 \cdot - 5)$

Step 3

Evaluate the result to find the discriminant.

Simplify each term.

Raise $- 4$ to the power of $2$ .

$16 - 4 (1 \cdot - 5)$

Multiply $- 4 (1 \cdot - 5)$ .

Multiply $- 5$ by $1$ .

$16 - 4 \cdot - 5$

Multiply $- 4$ by $- 5$ .

$16 + 20$

Add $16$ and $20$ .

$36$