Formulas: Variables in text and text equations

Using variables in the text

It is easy to insert values of variables directly in the text. All that is needed is to enclose the variable names with {}. Each text field has a scope of variables. All variables x of either number or string in the scope of the text can be used to replace the corresponding placeholder {x} in the text.

It is also possible to evaluate an expression and insert its value directly in the text by adding an equal sign at the beginning of the bracket such as {=x/1000}. This way is simpler if the named variables are not required. However, no error check is done unless the question is being instantiated in the quiz. An example is the rescaling of meters to kilometers below:

What is the speed of the rocket if it travels with distance {=x/1000} km in {t} s?

Using variables in text equations

Text equations are mathematical expressions or equations that are displayed in the text using math syntax such as:

• TeX
• MathML
• AsciiMath

See Equation Construction and Display for additional information on writing mathematical expressions.

Values of variables can be inserted in text equations in the same way as in the text, that is, by enclosing the variable names with {}. Values of expressions such as {=x/1000} can also be inserted.

TeX

Example

Write the following equation in TeX syntax. Upon display, {a}, {b} and {c} will be substituted by the value of these variables:

{a}x² + {b}x + {c} = 0

\( {a} x^2 + {b} x + {c} = 0 \)

MathML

Example

Write the following equation in MathML syntax. Upon display, {a}, {b} and {c} will be substituted by the value of these variables:

{a}x² + {b}x + {c} = 0

«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»
  «mn»{a}«/mn»
  «msup»«mi»x«/mi»«mn»2«/mn»«/msup»
  «mo»+«/mo»
  «mn»{b}«/mn»
  «mi»x«/mi»
  «mo»+«/mo»
  «mn»{c}«/mn»
  «mo»=«/mo»
  «mn»0«/mn»
«/math»

Tip

MathML equations are usually created with the aid of an editor. When creating the equation with an editor, it is easier to write a number, say 99, in lieu of the variables, for example:

«math xmlns=¨http://www.w3.org/1998/Math/MathML¨»
  «mn»99«/mn»
  «msup»«mi»x«/mi»«mn»2«/mn»«/msup»
  «mo»+«/mo»
  «mn»99«/mn»
  «mi»x«/mi»
  «mo»+«/mo»
  «mn»99«/mn»
  «mo»=«/mo»
  «mn»0«/mn»
«/math»

and then replace the numbers 99 by the variables {a}, {b} and {c} in the HTML code.

Example

Use variables and expressions in the equations of the main question text, the general feedback and the part's feedback. Use MathML syntax.

This Formulas question looks like this:

Note that the answers can be given as -5 and 3, or 3 and -5. See Multiple correct answers on the next page.

Play it    Login info  (Open in new tab: Ctrl+Shift+Click)

AsciiMath

Example

Write the following equation in the AsciiMath syntax. Upon display, {a}, {b} and {c} will be substituted by the value of these variables:

{a}x² + {b}x + {c} = 0

<script src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=AM_HTMLorMML"></script>
`{a} x^2 + {b} x + {c} = 0`

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