How do you solve #x^2 - x - 30 = 0# using the quadratic formula?

1 Answer
Feb 24, 2016

Answer:

See below for use of quadratic formula to obtain
#x=-5 or x=6#

Explanation:

For the general quadratic equation #ax^2+bx+c=0#
the quadratic formula:
#color(white)("XXX")x=(-b+-sqrt(b^2-4ac))/(2a)#
gives the solutions.

For the example: #x^2-x-30=0#
#color(white)("XXX")a=1#
#color(white)("XXX")b=-1#
#color(white)("XXX")c=-30#

Replacing the variables #a, b, c# in the general solution formula gives:
#color(white)("XXXX")x=(-(-1)+-sqrt((-1)^2-4(1)(-30)))/(2(1))#

#color(white)("XXXX")=(1+-sqrt(121))/2#

#color(white)("XXXX")=(1+-11)/2#

#rArr x=-5 or +6#