Why does entering a function of X(X+2) give an error message?
Normally the calculator will realise when you are using an ‘implied multiplication’ such as ‘3X’ meaning ‘3*X’, but sometimes gets confused (see right). You are probably already aware of the MATH button which contains a list of functions that can be used on the calculator. If so, then you must have noticed that each of them has to be used with brackets, like ROUND(3.23764,2) or SIN(35). The problem is that when you write X(X+2) the calculator thinks that you are trying to use a function called X, rather than multiply by X, and tries to evaluate the function X at the point X+2 along the same lines as evaluating f(x+2). When it finds that there is no such function it puts up the error message shown. The solution is simply to remember to put in the multiplication sign. . Most people also run across this problem in the Solve alplet at some stage. For example, if you enter the equation S=A(1-R^N)/(1-R) in order to solve a geometric progression problem then you will find that you will only g
