To find the equation of a line, all you need is a point and the slope. A polynomial function is not a rational function. 2 - 2x is not a quadratic function, since it lacks the constant term. If displacement is a linear function of time, then the slope of the graph represents the velocity. A real-valued function of a real variable is a rule that assigns exactly one number to each specified input number in a specified domain.
Some functions assign two or more numbers to each specified input number.
The regression line associated with a collection of more than two data points may pass through none of those points. The number 0.00346 is specified to 5 significant digits. When multiplying two numbers whose values are not known precisely, one should always round the answer to more significant digits than appear in the original factors.