Question 911619
y = -2(x^2+2x - 3) = -2(x^2+2x + 1) -1 -3) = -2(x+1)^2 +8
the vertex form of a Parabola opening up(a>0) or down(a<0), 
{{{y=a(x-h)^2 +k}}} 
where(h,k) is the vertex  and  x = h  is the Line of Symmetry

y = -2(x+1)^2 + 8
{{{drawing(300,300,   -6, 6, -6, 12, grid(1), blue(line(-1,12,-1,-6)) ,

graph( 300, 300, -6, 6, -6, 12,0, -2(x+3)(x-1) ) )}}}