Question 1180267
{{{y=-10(x^2+6x-8/10)}}}


Add and subtract  {{{(6/2)^2=9}}}, inside the parentheses.


{{{y=-10(x^2+6x+9-9-8/10)}}}


{{{y=-10((x+3)^2-90/10-8/10)}}}


{{{y=-10((x+3)^2-98/10)}}}


{{{highlight(y=-10(x+3)^2+98)}}}