How do you factor and solve #x^2 - x - 20 = 0#?

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Answer 1 · 2016-06-12T19:11:05

The solutions for the equation are: #color(blue)(x=-4, x = 5#

#x^2 - x - 20 = 0 #

The equation is of the form #color(blue)(ax^2+bx+c=0# where:

#a=1, b=-1, c=-20#

The Discriminant is given by:

#Delta=b^2-4*a*c#

# = (-1)^2-(4 * 1 * (-20))#

# = 1 + 80 = 81 #

The solutions are found using the formula:
#x=(-b+-sqrtDelta)/(2*a)#

#x = (-(-1)+-sqrt(81))/(2*1) = (1+- 9 )/2#

# x = (1+ 9 )/2 =10 /2, color(blue)( x= 5#

# x = (1 - 9 )/2 = -8/2 , color(blue)(x= - 4#