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Functions and Notation
Lesson 3
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Lesson 3: Function Evaluation

Interpret function notation as substitution.

Function notation means a rule. Evaluate by replacing the variable with the given input and simplifying in order.

Key formula

f(x)=ax+b⇒f(k)=ak+bf(x)=ax+b\Rightarrow f(k)=ak+b

Worked example

f(x)=5x+0,  f(−4)=−20f(x)=5x+0,\;f(-4)=-20

Checkpoint

If f(x)=5x−6, find f(−2)\text{If }f(x)=5x-6\text{, find }f(-2)

Recap

  • - f(x) names an output rule.
  • - Parentheses in f(k) indicate input, not multiplication.
  • - Use substitution carefully to avoid sign errors.
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