Diagram of simple filtration: oversize particles in the feed cannot pass through the lattice structure of the filter, while fluid and small particles pass through, becoming filtrate.
An odd function can be identified by replacing both the x and y values with -x and -y values. If the values in your equation are the opposite (positives are negatives and negatives are positives), then the function is odd. Take, for example, this equation y = x^2.
By definition: A function is strictly decreasing on an interval, if when x1 < x2, then f (x1) > f (x2). If the function notation is bothering you, this definition can also be thought of as stating x1 < x2 implies y1 > y2. As the x's get larger the y's get smaller.