Here Lorna constructs an account of her mistake of ‘adding 3’, which she had
originally thought was because she “guessed”. Now ‘after reading about algebra’,
she can see “x is squared plus 3 . . . you’re going to have it going plus 3 every time
but it’s got to be squared as well.” She reinforces this formulation of the function by
inverting it and emphasising the need for a square root.