More equations and formulae

More equations and formulae

Using and transforming formula

Learning objective

• Construct and transform more complex formulae

• Determine the restriction of variables in a formula

Literal equations

• Equations with several variables are called literal equations,

• eg: E = mc², etc

Changing the subject

• The subject of the equation is the variable isolated on one side

• For example, y is the subject of the equation y = mx + b.

• Rearranging an equation allows a different variable to be the subject.

• This is sometimes called solving the equation for a given variable.

Example

• Solve y = mx + b for x.

• Rearrange the equation to isolate x on one side: y – b = mx

• x= ( y - b ) /m

Restriction on variable

• Fractions, roots and some other operations can sometimes restrict the possible values for variables.

• For y = a/x, restriction is x not equal to 0

• For Vx, x must be greater than or equal 0