Question 1014918
A) a function with two real roots
.
{{{f(x)=x^2-4)}}}
Graph crosses x axis twice.
(blue line on graph below)
.
B) a function with one real root
.
{{{f(x)=x^2}}}
Graph just touches x axis once (vertex on x axis)
(Green line on graph below)
. 
C) a function with two complex roots 
.
{{{f(x)=x^2+4}}}
Graph does not touch or cross x axis.
(Red line on graph below)
.
GRAPH:
.
{{{ graph( 800, 800, -10, 10, -10, 10, x^2+4, x^2, x^2-4) }}}