Question 52431
x^2-4x-5=0
Factoring:  Two numbers that multiply together to give you -5 but add together to give you -4 are -5 and +1.
(x-5)(x+1)=0
x-5=0
x-5+5=0+5
x=5
x+1=0
x+1-1=0-1
x=-1
x=-1 and x=5
_________________________________
Complteting the square:
x^2-4x-5=0
x^2-4x-5+5=0+5
x^2-4x=5
x^2-4x+(-4/2)^2=5+(-4/2)^2
x^2-4x+(-2)^2=5+(-2)^2
x^2-4x+4=5+4
(x-2)^2=9
sqrt((x-2)^2)=(+or-)sqrt(9)
x-2=(+or-)3
x-2+2=+2(+or-)3
x=2(+or-)3
x=2-3=-1
x=2+3=5
x=-1 and x=5
----------------------------------------
x^2-4x-5=0
a=1;b=-4;c=-5
{{{x=(-b+-sqrt(b^2-4*a*c))/(2*a)}}}
x=(-(-4)+or-sqrt((-4)^2-4*(1)*(-5))/(2*1)
x=(4+or-sqrt(16+20))/2
x=(4+or-sqrt(36))/2
x=(4+or-6)/2
x=(4-6)/2
x=(-2)/2
x=-1
x=(4+6)/2
x=10/2
x=5
x=-1 and x=5