# Math Concepts

**Topics:**Number, Elementary arithmetic, Convex function

**Pages:**2 (351 words)

**Published:**December 12, 2012

12/10/12

p. 3

Chapter 4 paper

In this chapter one of the first things we learned was that you can make complex equations look simpler by making substitutions. Take the equation: 2tan2-3tan-2=0

To make this look simpler you can substitute u for tan to get: 2u2-3u-2=0

From there you can us the quadratic formula to get:

u= -0.5, 2

With this you can now say tan=2 and tan=-0.5 which makes solving for much easier. In this case substitutions made solving much easier and less chaotic looking.

The next thing we learned was to rewrite equations in a way that suits your purpose. One key skill for rewriting equations is to get rid of negative exponents. The equation (x-1+y-2 )/(x+y) can be simplified to get rid of the negative exponents. X-1 =1/x therefore: (x-1+y-2 )/(x+y)=(1/x)+(1/y2/(x+y)

From there you can simplify it further by multiplying the top and bottom by a common factor, in this case it is: x+y2 So to finish simplifying the equation you take:

(1/x)+(1/y2/(x+y)

And multiply it by (x+y2)/(x+y2) to get:

(Y2+x)/(x2y2)/(xy3)

Other common rewrite is to rationalize the denominator or numerator. This is very helpful for solving equations with a square root on the bottom. Example: (3)+2/(3)+1

To rationalize this you multiply the numerator or denominator (which ever one you want to rationalize) by its difference of squares. For this:

To rationalize the denominator you multiply it by ((3)-1)/ ((3)-1) Giving you: 1+3/2.

Another thing we learned was how to tell when a graph is concave up or down and decreasing or increasing. A graph is concave up when the x values are above the x axis and concave down when they are below. A graph is Increasing when you increase the y value and the x value increases and its decreasing when the x value decrease.

Examples:

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