Final Review: Other Techniques

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Final Review: Other Techniques

• Evaluating algebraic expressions

• Evaluating functions

• Finding composite functions ( f ◦ g )( x ) = f ( g ( x ))

• Checking inverse functions

To check if f and g are inverse function of each other, you need to check:

1.

f ( g ( x )) = x

2.

g ( f ( x )) = x

3. domain of f = range of g

4. domain of g = range of f

• Finding inverse function

1. In a equation of f ( x ), replace f ( x ) by y .

2. Solve this equation for variable x in terms of y .

3. Replace x by f − 1 ( y ).

4. Replace all y ’s by x ’s.

• Finding domain and range of a function

Domain of:

– rational function: all x such that the denominator is not 0

– radical function: all x such that the radicand > 0 when the index is even all real numbers when the index is odd

– exponential function: all real numbers

– logarithmic function: all x such that the logarithm is applied on a positive number

Range of:

– a x ( a > 0 , a = 1): all positive numbers

– log a x ( a > 0 , a = 1): all real numbers

• Factoring polynomials

1. Common monomial factor

2. By grouping (4 terms)

3. Special product

(a) difference of two squares: u 2 − v 2 = ( u + v )( u − v )

(b) sum of two cubes: u 3 + v 3 = ( u + v )( u 2 − uv + v 2 )

(c) difference of two cubes: u 3 − v 3 = ( u − v )( u 2 + uv + v 2 )

4. Trinomial (3 terms)

5. Repeatedly checking if any of the above four methods can be applied on each factor until none of them can be applied.

• Long division and synthetic division of polynomials

Compare with the long division between integers.

Synthetic division only works for the divisor of the shape x − k .

• Completing the square

Only works for quadratic expression with leading coefficient 1.

So factor out the leading coefficient first.

• Constructing algebraic expressions from verbal description (see § 1.5 for keywords)

• Solving word problems

1. Establish a word equation from the problem

2. Assume one unknown number to be x

3. Develop expressions for other unknown numbers in x from the problem

4. Solve the equation for x .

5. Check if your solution makes sense in the problem (such as a negative distance)

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