Evaluate Expressions

6.AT.6c · Unit 6 · Lesson 2

Name   Period

Objectives / Objetivos

Content Objective: I can evaluate algebraic expressions by substituting values for the variables.

Language Objective: I can explain my steps using the words variable, expression, evaluate, and substitute.

Key Idea / Idea clave

Replace the variable with its number, then follow the order of operations to find the total.

I Notice / Observo

  • What does the 150 represent in the expression?
  • What does the 12s represent?

I Wonder / Me pregunto

  • What if speakers cost $15 each instead?

Vocabulary / Vocabulario

Term / TérminoDefinition / Definición
Variable
Variable		A letter that stands for a number that is unknown or can change.
Una letra que representa un número desconocido o que puede cambiar.
Expression
Expresión		A math phrase with numbers and letters, but no equal sign.
Una frase matemática con números y letras, pero sin signo igual.
Evaluate
Evaluar		To find the value by putting numbers in for the letters.
Encontrar el valor poniendo números en lugar de las letras.
Substitute
Sustituir		To put a number in place of a letter.
Poner un número en lugar de una letra.
Coefficient
Coeficiente		The number in front of a letter, like the 3 in 3x.
El número frente a una letra, como el 3 en 3x.
Like terms
Términos semejantes		Terms with the same letter raised to the same power, like 2x and 5x.
Términos con la misma letra elevada a la misma potencia, como 2x y 5x.

Practice Preview / Vista previa de práctica

  1. Evaluate 3x + 7 when x = 4.
    1. 19
    2. 34
    3. 12
    4. 14
  2. Evaluate each expression for the given value of the variable.
  3. Evaluate each expression when a = 3. Sort by whether the result is greater than 15 or not.
  4. Find the Evaluation Error
    1. Step 1: Expression — 4x² + 3 when x = 2
    2. Step 2: Substitute — 4(2)² + 3
    3. Step 3: Apply exponent — (4 × 2)² + 3 = 8² + 3
    4. Step 4: Calculate — 64 + 3 = 67

    Which step has the mistake? Explain it and write the correct work.

Reflection / Reflexión

One thing I learned today / Una cosa que aprendí hoy: