Question 34282
I am assuming that you want the value of a.
{{{a^2+8a+15=0}}} Set equation equal to zero
{{{(a+3)(a+5)=0}}}Factor
{{{a+3=0}}}
{{{a=-3}}}  
{{{a+5=0}}}
{{{a=-5}}}
Thus, the answer is {{{a=-3}}} or {{{ a=-5}}}

Smiles,
lyra