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Mathematics vocabulary · Algebra and Equations

Plug in

Meaning in mathematics, with examples

phrasal verbCommon term

In mathematics, plug in means: To put a particular number in place of a variable in a formula or expression to see what result it gives; an informal word for 'substitute'.

In Turkish: yerine koymak, yerine yazmak

How it is used

Very common in spoken classroom English: 'plug in x = 2', 'plug the values into the formula', 'plug it back in to check'. In formal writing 'substitute' is preferred: 'Substituting x = 2 gives…'.

Example sentences

  1. Plug in x = 3 and see if both sides are equal.

  2. Once you have the radius, just plug it into the area formula.

Common collocations

  • plug in a value
  • plug into the formula
  • plug it back in
  • plug in and check
  • variableA letter or symbol, such as x or y, that stands for a number which can change or which you do not know yet.
  • solveTo find the value or values of an unknown that make an equation or inequality true, or to find the answer to a problem.
  • f of xThe usual spoken form of f(x), the output of a function f when the input is x; for example, if f(x) = x + 5, then 'f of 2' is 7.
  • expressionA combination of numbers, variables and operation signs, such as 4x² − 3x + 7, that has no equals sign and can be simplified or evaluated.

More terms: Algebra and Equations

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