Question 1179959
the line of  symmetry passes through the vertex

first, write your equation in vertex form

{{{y= a(x- h)^2 +k}}}

{{{y= (x^2 + 16x) + 60}}}.......complete square
{{{y= (x^2 + 16x+8^2) -8^2+ 60}}}
{{{y= (x +8)^2 -4}}}-> in this case {{{ a=1}}}


{{{ drawing( 600, 600, -15, 15, -15, 15,
green(line(-8,10,-8,-10)),
graph( 600, 600, -15, 15, -15, 15, (x +8)^2 -4)) }}}


the equations of three different quadratics:

1.

{{{y= a((x+ 8)^2 -4)}}}........let {{{a=2}}}
{{{y= 2(x+ 8)^2 -8}}}
{{{y= 2x^2 + 32x + 120}}}

{{{ drawing( 600, 600, -15, 15, -15, 15,
green(line(-8,14,-8,-14)),
graph( 600, 600, -15, 15, -15, 15, 2x^2 + 32x + 120)) }}}




2.

{{{y= a((x+ 8)^2 -4)}}}.......let {{{a=-2}}}
{{{y= -2(x+ 8)^2 -8}}}
{{{y= -2x^2 - 32x - 136}}}

{{{ drawing( 600, 600, -15, 15, -15, 15,
green(line(-8,14,-8,-14)),
graph( 600, 600, -15, 15, -15, 15, -2(x+ 8)^2 -8)) }}}



3.

{{{y= a((x+ 8)^2 -4)}}}.......let {{{a=5}}}
{{{y= 5((x+ 8)^2 -4)}}}
{{{y= 5(x+ 8)^2 -20}}}
{{{y= 5x^2 + 80x + 300}}}


{{{ drawing( 600, 600, -15, 15, -20, 15,
green(line(-8,14,-8,-20)),
graph( 600, 600, -15, 15, -20, 15, 5(x+ 8)^2 -20)) }}}