Question

There are some values of a, b, c for which the equation ax + by + c = does not represent a straight line. Give an example of such values.

Answer 1

one of the restrictions for ax+by+c=0 to be a line is
\(a \ne 0 \: and, \: b\ne0 \)
so , if a=b=0, ax+by+c does not represent a line.
it just represents a constant c.

Answer 2

i meant \(a \ne 0 \: and, \: b\ne0 \: \: simultaneously\)