Evaluating Functions, Algebra 1 lesson packet and Teacher Deck (HSF.IF.A.2)
HSF.IF.A.2 Algebra 1 Unit 4: Introduction to Functions

Evaluating Functions

I can put an input into a function rule in parentheses, signs and all, and tell evaluating from solving.

What students learn

Students learn to evaluate a function for any input, writing it in parentheses so its sign goes in too, and tell finding f(a) from finding the x that gives f(x) = k.

See inside

The key rule

Write the input in parentheses wherever x is. In f(7) the 7 goes in; in f(x) = 7 the 7 is the output, so solve.

f(−4) → (−4)², never −4²

Before you start, ask which side of the = the number is on.

Watch out

g(x) = x² + 2. Find g(−5).

The mistake: g(−5) = −5² + 2 = −23−5² squares only the 5.

The fix: g(−5) = (−5)² + 2 = 25 + 2 = 27(−5)² = 25: the sign is squared too.

The mistakes it targets

  • Squares a negative input without parentheses
  • Substitutes a number that is the output as the input
  • Solves for x when the number is the input
  • Drops a minus sign when two negatives meet

The interactive Teacher Deck (31 slides, PowerPoint)

  • The Learn page taught on screen: 8 fill-in blanks, each filled on its own click as students write it
  • The worked example one slide per step (three steps), each with the reason for the step
  • Six practice and three apply problems: a your-turn slide with a think-time bar, then the solution one line per click
  • Jump buttons on every slide: go straight to any problem, the answer bank or the exit ticket
  • Speaker notes on each problem: the question to ask, the worked answer and the common error to listen for
  • A completed deck PDF (19 pages) with every slide fully built, to print or post

The student packet (9 pages)

  • Learn: guided notes with four definitions, the key rule, a worked example and a Watch Out error pair
  • Practice: two warm-up, two standard and two stretch problems, with an answer bank for self-checking that hides three common-mistake decoys
  • Apply: one word problem, a reasoning prompt and one error analysis
  • Assess: an exit ticket of four items, two per page, with an I-can self-rating
  • Homework (page 5): eight new problems, two warm-up, four standard and two stretch
  • Answer key (pages 6–7): every problem worked step by step, four common mistakes with what to do about each, and a grading guide, plus the homework key (page 8)
  • Color and ink-saver editions of the whole packet

Standard codes refer to the Common Core State Standards for Mathematics. Math Class 678 is an independent publisher, not affiliated with, sponsored by, or endorsed by NGA Center or CCSSO. Every product is sold on Teachers Pay Teachers.