Chapter 1.2, Problem 9E

Determine whether each statement qualifies as a definition.
(a) $y=f(x)$ is a linear function if its graph is a straight line.
(b) $y=f(x)$ is a quadratic function when it contains an x2 term.
(c) A quadrilateral is a square when all its sides have equal length.
(d) A triangle is a right triangle if the sum of two of its interior angles is $\text{9}0°$ .
(e) Two lines are parallel when their slopes are the same number.
(f) A quadrilateral is a rectangle if all its interior angles are equal.