The equation x2 - 5x - 24 = 0 can be factored as (x-8)(x+3) = 0, so we know the solutions are x=8 and x=-3. Here's the solution using the quadratic formula.
For ax2+bx+c = 0, the solutions are given by
x = (-b ±√(b2-4ac))/(2a)
Your equation has a=1, b=-5, c=-24.
x = (-(-5) ±√((-5)2 - (4)(1)(-24))/(2*1)
= (5 ±√(25 + 96))/2 = (5±√121)/2 = (5±11)/2
x = 16/2 or -6/2
x = 8 or -3
For ax2+bx+c = 0, the solutions are given by
x = (-b ±√(b2-4ac))/(2a)
Your equation has a=1, b=-5, c=-24.
x = (-(-5) ±√((-5)2 - (4)(1)(-24))/(2*1)
= (5 ±√(25 + 96))/2 = (5±√121)/2 = (5±11)/2
x = 16/2 or -6/2
x = 8 or -3