If the weight force of an object is given by F=mg, what is the combined weight force of two of these objects with mass my and my? The solution to this will simply be the sum of the two weight forces gx (mı + m2). Notice that this is an algebraic expression in three variables, the expression can be written expanded as gmı +9m2. In this solution, we want to enter the expression in such a way that it is clear and unambiguous. Notice that if we have a function gevaluated at a point mı + m2 this would be expressed as g(mı + m2). How does STACK tell the difference? One is an example of multiplication and the other is a function evaluation. Multiplication requires the use of the star * to tell STACK to multiply the two elements Enter the correct answer of g* (m_1 + m_2) in the box below. Notice that STACK sees three variables here, g, m, and m2. Now, try and enter g (m_1 + m_2). Notice that this time, STACK sees 2 variables, me and my, but it thinks that gis a function, as you have written it using STACK function syntax. One important thing to note, it doesn't actually matter the order you enter an expression, STACK is smart enough to tell when (most) things are equivalent. For example, our solution is gx (ma + m2), but an answer of g*m_1 + g*m_2 would also be correct. Check