A quadratic expression has the general form:
[tex]\begin{gathered} ax^2+bx+c \\ \text{where }a\ne0 \end{gathered}[/tex]In the expression:
[tex]\begin{gathered} 5x^2-18 \\ a=5,b=0\text{ and c=-18} \end{gathered}[/tex]So, is a quadratic expression beacuase satisfy the general formula with a = 5 (distinc of zero), b=0 and c=-18.
