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Algebraic notation and substitution
Lesson 31 of 75
Introduction

The language of algebra

Objective. Use variables, terms, coefficients and constants correctly.

  1. 1. Learn
  2. 2. Worked example
  3. 3. Practice
  4. 4. Feedback
  5. 5. Continue

Learn: the key idea

Algebra uses letters called variables to stand for numbers that can change or are currently unknown. A term is a single number, variable, or product of numbers and variables, such as 5x or 3. A coefficient is the number multiplying a variable, so in 7y the coefficient is 7, while a constant is a term with no variable attached, like the 4 in x+4. An expression such as 3x+2y−5 combines several terms using addition or subtraction, without an equals sign, unlike an equation.

Worked example

In the expression 6x + 3y − 7, identify the coefficients and the constant term.

In the expression 6x + 3y…
Illustrated card showing In the expression 6x + 3y − 7
  1. 1Find the term attached to x: 6x, so the coefficient of x is 6.
  2. 2Find the term attached to y: 3y, so the coefficient of y is 3.
  3. 3Find the term with no variable: −7.
  4. 4This −7 is the constant term.

Answer: Coefficients 6 and 3; constant term −7

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Practice

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Common mistake. Pupils often confuse a coefficient with a constant, thinking the 4 in 4x is a separate number term rather than part of the term 4x. Point out that a coefficient always sits attached to a variable.

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