To rationalise a surd means to manipulate a fraction involving terms which are being square rooted so that no term in the denominator is being square rooted. For this example 2/root(x) we multiply the fraction by root(x)/root(x). We can do this because something divided by itself is equal to 1, and you can multiply anything by 1 without changing its value.To do this we start with the numerator. 2 multiplied by root(x) which is equal to 2(root(x). Then we do the same with the denominator. root(x) multiplied by root(x) which is just equal to x. This is because the square root of something, squared cancels out the square root. Therefore:2/root(x) x root(x)/root(x) = 2(root(x)/xWith 2(root(x)/x being the rationalised answer.