First, we need to declare the unknown, as usual we will use x for the number. Then, the square of the number will be x^2. Following the order of the statement we have that x + x^2 =42. Here we have ‘‘translated’’ the term <em>the sum</em> in the mathematical operation of addition. Moreover, we convert the fact that the sum of a number and its square is 42 in a equality. This is the explanation of the equation x + x^2 =42.
Finally, using that the addition is commutative we have that x^2+x=42.
