I squared a number… Let's call the desired result n, and the initial number x. From the statement, we have that n = (x 2 -–) / x. With factorization we find that: n = (x -– 1). x / x. Simply put, we have n = x -– 1, or number minus 1. Back to statement Challenge 37 What percentage of boys?

Addition Given the matrices, we call the sum of these matrices the matrix, such that C ij = a ij + b ij, for all: A + B = C Examples: Note: A + B exists if and only if A and B are of the same kind. Properties Being A, B and C matrices of the same type (mxn), we have the following properties for the addition: a) commutative: A + B = B + A b) associative: (A + B) + C = A + (B + C) c) neutral element: A + 0 = 0 + A = A, where 0 is the null matrix mxnd) opposite element: A + (-A) = (-A) + A = 0 Subtraction Given the matrices, we call difference between these matrices the sum of A with the opposite matrix of B: A - B = A + (- B) Note: Next: Multiplying a Real Number by a Matrix

UNION - Set of all elements belonging to two or more sets. It is also called a meeting. UNIT - The quantity that is the reference in the measure In the case of numbering 1 is the unit used. UNITARY - Set that has a single element. UNIVOCA - Match that makes an object match one and only one image.