Explanations:
Note that any expression of the form:
[tex]ax^2\text{ + bx + c}[/tex]is a quadratic polynomial.
The given equation in the question is:
[tex]Y=x^2\text{ - 5x + 6}[/tex]Comparing the given equation with the general expression I wrote above:
a = 1, b = -5 and c = 6.
Since the given equation takes the form of the general expression, it is therefore quadratic.