^{2}± cx = n by trial and improvement.

The resource includes

- An interactive Excel spreadsheet
- Instructions for using the spreadsheet
- Lesson notes for teachers

^{2}+ x = 20. The spreadsheet accepts as correct answers accurate to three decimal places.

The activity allows pupils to try to refine a solution to an equation of the form ax

^{2}± cx = n by trying different values of x. The equation can be changed to cater for a range of prior knowledge. The activity encourages thinking about the effects on the solution of changing the value of x.

The activity provides opportunities for:

- whole class teaching
- paired work
- oral work as pupils justify subsequent attempts in the light of previous outcomes.

**Download resources**