Question 1031481
Try to factorize the function if possible; or look at discriminant:


{{{(-3)^2-4*2*(-20)}}}
{{{9+8*20}}}
{{{9+160}}}
{{{169}}}
{{{13^2}}}


If you use general solution for quadratic expression,
zeros are  {{{(3+- 13)/4}}}
{{{-10/4=highlight(-5/2)}}}
or
{{{16/4=highlight(4)}}}
The two zeros.