Question 48286
{{{7r^2 + 24r = -15}}}
{{{r^2 + 24r/7 = -15/7}}}
{{{(r + 12/7)^2 = -105/49 + 144/49 = 39/49}}}
{{{r + 12/7}}} = +-{{{sqrt(39)/7}}}
{{{r = -12/7 +- sqrt(39)/7}}}
{{{r = (-12 +- sqrt(39))/7}}}