added review01-04 to chapter13

Author: trapperdot00

Chapter13/review/01.txt

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+A function of one argument is a function that takes one parameter.
+Whether it does something with that argument is up to the function.
+
+For example, the horizontal line function discards the given argument,
+by not even naming the variable, only the type of it, and returns one for every value given;
+however the sloping line returns the argument multiplied by 0.5.
+
+The graphics type, Function, takes a function that takes one argument of type double, and returns double.
+
+We use continuous lines for visualizing functions of one argument.

Chapter13/review/02.txt

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+We would use a continuous line for representing data when one value was somehow a function of an other.
+
+We would use discrete points if the values were not functions of each other.

Chapter13/review/03.txt

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+The function y=mx+b defines a slope.

Chapter13/review/04.txt

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+A parabola is a graph of the quadratic formula: y=ax^2+bx+c.
+It is approximately U shaped, symmetrical to the y-axis, and can also point downwards.
+It has a minimum or maximum point, from which in each direction, its value grows or lessens.
+Its curve's slope is increasing or decreasing as we get further from its min/max point.