Changing The Subject
Equations and formulae sometimes need to be rearranged. Another way to describe it is "changing the subject". When we write an equation it has a subject, so for example with y = mx + c, y is the subject. With x = 2y - 4 then x is the subject. This is a very important skill when accessing more advanced topics such as those met at A-Level Mathematics.
The image below asks which shows b as the subject? The answer is b = ac + 25.
The image below as which shows p as the subject?
Which shows y in terms of x?
Formulas and equations sometimes need to be rearranged. When solving equations the subject is usually changed so that we are finding the unknown with letter "x". Equations can be rearranged with or without brackets. Sometimes students will have to simplify the expression before rearranging the equation. The image below states the question as make t the subject of the equation. The question can be phrased in two other ways. Take a look at the alternatives.
What question could be asked for each solution below? Rearrange the equation so that t is the subject or make t the subject of the equation.
The examples below rearrange the equations such that t is written in terms of s. Take a look at the solutions. Notice that when the subject is negative, we multiply it by negative 1, or add the variable to both sides, also known as "swapping sides".
For the example below we multiply both sides by 4. The equation looks like 44s = t². To express t in terms of s we square root both sides. Square root is the inverse operation for square numbers.
Rearranging Formulae Worksheets – New & Engaging