Indicate whether the statement is true or false. 15. A difference quotient is used to calculate the slope of the secant at a general point. 16. The instantaneous rate of change is determined by finding the difference quotient over a very small interval. 17. A limit exists if both the right-hand and left-hand limits are equal. 18. A jump discontinuity occurs when a function jumps over the x-axis. 19. An infinite discontinuity means a function is merely a set of scattered points. 20. A vertical asymptote can be found by solving the numerator equal to zero in a rational function. 21. A piecewise function always has a jump discontinuity. 22. Functions that have an indeterminate form when evaluating a limit can always be simplified by factoring