Question 24374
Ok, heres what you do. Your questions is x²-4x-5=0

By factorizing
x²-4x-5=0
(x-5)(x+1)=0 
and there would be two answers
1)	x-5=0
        x=5
2)	x+3=0
         x=-1

By completing of square 
x²-4x-5=0
x²-4x    =+5
x²-4x+(4/2)²=5+(4/2)²
x²-4x+(2)²   =5+(2)²
(x-2)(x-2)    =5+4
         (x-2)²  =9
          x-2     = +or- (square root of 9)
          x-2     =+or-(3)
 and there will be 2 answers as well
1)x=3+2
   x=5
2)x=-3+2
   x=-1

By formula.
Formula of to solve the above equation is


{{{x = (--4 +-sqrt( -4^2-4*1*-5 ))/(2*1) }}}
={{{x = (+4 +-sqrt( 16+20))/(2) }}}

={{{x = (4 +-sqrt( 36 ))/(2) }}}
=(4+or-6)/2
this also got 2 answers as well
1)x=(4+6)/2
  x=10/2
  x=5

2)x=(4-6)/2
  x=-2/2
  x=-1

therefore your answers are 5 or -1
(dont be surprised that i am a secondary pure science stream student)
yh_tong