# Doro68: 3.5 Functions Strategy

### 8 terms by Darowell

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### Numerical Substitution: f(x)=x^2-2

f(x) = 5 ; 25-2 = 23

### Variable Substitution: f(x) = (w+6)

x^2-1/2 = (w+6)^2 - 1/2

### Compound Functions: f(g(x))

Solve the inner equation then use result in outer equation.

### Functions with Unknown Constants: If f(x)=ax^2-x and f(4)=28, what is f(-2)?

1. Solve for the unknown, in this case "a"
2. Rewrite the function. replacing the constant with numerical value.
3. Solve function for the new input variable.

### Function Graphs: Graph the function, f(x)=-2x^2+1

Use x inputs to determine y coordinates, then map.

### Common Function Type #1: Direct Proportionality - Set up ratios for the "before" case and the "after" case, and then set the ratios equal to each other.

i.e. y=kx > k=y/x

### Common Function Type #2: Indirect Proportionality - Set up products for the "before" case and the "after" case, and then set the products equal to each other.

i.e. y=k/x , k=xy

i.e. y=mx+b

Example: