x^2+2=18, find the value of x.

This is a basic rearranging of the equation that easily catches students out and will generally be offered 3 marks. The first thing to do is take the 2 on the other side of the equation so we get x^2=16. From this points all we have to do is take root of 16. However what students easily forget is that there are always 2 roots of positive numbers one being the original root and one being its negative counterpart. Experienced students should remember this and thus get the answer that x=4 or x=-4.