Question

ax^2 + bx + c = 0, what happens when a = 0? What kind of graph will you get, and explain why?

Answer 1

on putting a=0, we get
bx+c=0
=> x=-c/b
which is the equation of a straight line.
So, the graph is a vertical line intersecting the X-axis at x=-c/b

Answer 2

y=ax^2+bx+c
of a=0
then
y=bx+c
which is a line