Question 1100471
Trying "intercept form",

{{{y=a(x-r)(x-s)}}} for roots or zeros r and s,


{{{a(x+8)(x-1)=0}}}, according to the two given roots.


The other given point:
{{{a(x+8)(x-1)=y}}}
{{{a(2+8)(2-1)=-20}}}
{{{a*10*1=-20}}}
{{{10a=-20}}}
{{{highlight(a=-2)}}}


The equation for the three given points is  therefore {{{highlight(y=-2(x+8)(x-1))}}}.


You can decide for yourself if using the intercept method is better and discuss it.  We only needed to handle two equations using the intercept form.