The functions y1(t)=e8t\displaystyle {y}_{{1}}{\left({t}\right)}={e}^{{-{8}{t}}} and y2(t)=e11t\displaystyle {y}_{{2}}{\left({t}\right)}={e}^{{-{11}{t}}} are known to be solutions of the equation below. Fill in the blanks to complete the equation.

y+\displaystyle {y}{''}+   y+\displaystyle {y}'+   y=0\displaystyle {y}={0}