F (x) = x^2-3x-15 what's the root

There are two roots:

(3 + √69) / 2 and (3 - √69) / 2

Step-by-step explanation:

Use the quadratic equation to solve this ...

x = [-b ± √ (b² - 4ac) ] / (2a)

Here, a = 1, b = - 3, and c = - 15, plug them in and simplify

x = ([ - (-3) ± √[ (-3) ² - 4 (1) (-15) ]) / [2 (1) ]

x = (3 ± √[9 - (-60) ]) / 2

x = (3 ± √69) / 2

so

x = (3 + √69) / 2 and x = (3 - √69) / 2