A quadratic function is any function that can be written in the form:
y = ax^2 + bx + c ;
where a, b, and c are real numbers and a = 0
A/ expression doesn't have x^2, so it's wrong
B/ y = (x-5)^2 = x^2 - 2.5.x + 5^2 = x^2 - 10x + 25
<=> y = x^2 - 10x + 25
So B is quadratic function
As for C and D they're not quadratic functions
