Mathematics » Introducing Integers » Subtract Integers

Evaluating Variable Expressions with Integers

Evaluating Variable Expressions with Integers

Now we’ll practice evaluating expressions that involve subtracting negative numbers as well as positive numbers.

Example

Evaluate \(x-4\phantom{\rule{0.2em}{0ex}}\text{when}\phantom{\rule{0.2em}{0ex}}\)

  1. \(\phantom{\rule{0.2em}{0ex}}x=3\phantom{\rule{0.2em}{0ex}}\)
  2. \(\phantom{\rule{0.2em}{0ex}}x=-6.\)

Solution

To evaluate \(x-4\) when \(x=3\), substitute \(3\) for \(x\) in the expression.

 Evaluating Variable Expressions with Integers
Evaluating Variable Expressions with IntegersEvaluating Variable Expressions with Integers
Subtract.Evaluating Variable Expressions with Integers

To evaluate \(x-4\) when \(x=-6,\) substitute \(-6\) for \(x\) in the expression.

 Evaluating Variable Expressions with Integers
Evaluating Variable Expressions with IntegersEvaluating Variable Expressions with Integers
Subtract.Evaluating Variable Expressions with Integers

Example

Evaluate \(20-z\phantom{\rule{0.2em}{0ex}}\text{when}\phantom{\rule{0.2em}{0ex}}\)

  1. \(\phantom{\rule{0.2em}{0ex}}z=12\phantom{\rule{0.2em}{0ex}}\)
  2. \(\phantom{\rule{0.2em}{0ex}}z=-12\)

Solution

To evaluate \(20-z\phantom{\rule{0.2em}{0ex}}\text{when}\phantom{\rule{0.2em}{0ex}}z=12,\) substitute \(12\) for \(z\) in the expression.

 Evaluating Variable Expressions with Integers
Evaluating Variable Expressions with IntegersEvaluating Variable Expressions with Integers
Subtract.Evaluating Variable Expressions with Integers

To evaluate \(20-z\phantom{\rule{0.2em}{0ex}}\text{when}\phantom{\rule{0.2em}{0ex}}z=-12,\phantom{\rule{0.2em}{0ex}}\text{substitute}\phantom{\rule{0.2em}{0ex}}-12\phantom{\rule{0.2em}{0ex}}\text{for}\phantom{\rule{0.2em}{0ex}}z\phantom{\rule{0.2em}{0ex}}\text{in the expression.}\)

 Evaluating Variable Expressions with Integers
Evaluating Variable Expressions with IntegersEvaluating Variable Expressions with Integers
Subtract.Evaluating Variable Expressions with Integers

Optional Video: Subtracting Integers

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