Question 148758
Simply use the coefficients in the Quadratic Formula:



{{{x = (-b +- sqrt( b^2-4ac ))/(2a)}}} Start with the quadratic formula



{{{x = (-(8) +- sqrt( (8)^2-4(1)(15) ))/(2(1))}}} Plug in  {{{a=1}}}, {{{b=8}}}, and {{{c=15}}}



{{{x = (-8 +- sqrt( 64-4(1)(15) ))/(2(1))}}} Square {{{8}}} to get {{{64}}}. 



{{{x = (-8 +- sqrt( 64-60 ))/(2(1))}}} Multiply {{{4(1)(15)}}} to get {{{60}}}



{{{x = (-8 +- sqrt( 4 ))/(2(1))}}} Subtract {{{60}}} from {{{64}}} to get {{{4}}}



{{{x = (-8 +- sqrt( 4 ))/(2)}}} Multiply {{{2}}} and {{{1}}} to get {{{2}}}. 



{{{x = (-8 +- 2)/(2)}}} Take the square root of {{{4}}} to get {{{2}}}. 



{{{x = (-8 + 2)/(2)}}} or {{{x = (-8 - 2)/(2)}}} Break up the expression. 



{{{x = (-6)/(2)}}} or {{{x =  (-10)/(2)}}} Combine like terms. 



{{{x = -3}}} or {{{x = -5}}} Simplify. 



So our answers are {{{x[1] = -3}}} or {{{x[2] = -5}}}  (note: the order does <font size=4><b>not</b></font> matter)