Question 120096
This is a case where you use the quadratic equation and make
sure that the discriminant, which is {{{b^2 - 4ac}}} is zero
That guarantees that there is only one solution.
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
where equation is in the form {{{ax^2 + bx + c = 0}}}
{{{8x2 + kx + 7 = 0}}}
{{{a = 8}}}
{{{b = k}}}
{{{c = 7}}}
{{{b^2 - 4ac = 0}}}
{{{k^2 - 4*8*7 = 0}}}
{{{k^2 - 224 = 0}}}
{{{k^2 = 224}}}
{{{k = sqrt(224)}}}
{{{k = sqrt(14*16)}}}
{{{k = +4*sqrt(14)}}} answer
{{{k = -4*sqrt(14)}}} answer