Explanation:
x^2 + (1) x - 6 = 0 for completing the square , the x^2 coefficient has to be '1' .....and it is for this quadratic equation....now take one half OF THE x COEFFECIENT ....this coefficient is '1' also.....one half of it is 1/2
then square this = 1/4 then add it and subtract it from the equation:
x^2 + x + 1/4 - 1/4 -6 = 0 now you can reduce the underlined portion
(x+1/2)^2 - 1/4 - 6 = 0 add 1/4 and 6 to both sides of the equation
(x+1/2)^2 = 6 1/4 sqrt both sides ( 6 1/4 = 25/4 BTW)
x + 1/2 = +- sqrt ( 25/4)
x + 1/2 = +- 5/2 Now subtract 1/2 from both sides
x = - 1/2 +- 5/2 = 2 or -3