Question 390011
Find a if x^2-5x + a = 0 has equal roots. 
Just like completing square; divide the coefficient of x by 2 and square it
x^2 - 5x + {{{25/4}}} = 0 (a = {{{25/4}}})
Factors to
(x - {{{5/2}}})(x - {{{5/2}}})
x = {{{5/2}}}