Writing and Solving Equations

You might not have to just solve equations in your exam - you might have to write them out first!

Remember an equation just says that two expressions are equal.

So you just need to write out the information you read, and make sure you include an '=' sign!

Here's an example:

"I think of a number, double it and add seven. My answer is 37.

A number we don't know is usually called x.

Double this number would be written as 2x.

Seven more than this must be 2x + 7.

We are told this equals 37, so we write 2x + 7 = 37.

Got the hang of it? Try writing an equation for each of these sentences:

Using the Quadratic Formula

Whenever you're faced with a quadratic equation you have choice:

• Plot it and find the intercepts
• Factorise and solve (x+...)(x+...) etc. Each bracket =0 etc
• Complete the square and rearrange (see these older posts)
• Use the quadratic formula:

(More can be seen about the quadratic formula in this post)

You will have your own order of preference for the above methods, but one thing you can be certain of is that if there are real solutions, the formula will find them (factorising may not!).

Mean from a Frequency Table and Grouped Data

Calculating the mean from a frequency table appears on both foundation and higher GCSE papers. Here are a couple of questions to have a go at and a video to help. 

Calculate the mean