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For n = 40, it produces a square number, 1681, which is equal to 41 × 41, the smallest composite number for this formula for n ≥ 0. If 41 divides n , it divides P ( n ) too. Furthermore, since P ( n ) can be written as n ( n + 1) + 41, if 41 divides n + 1 instead, it also divides P ( n ).
For example, if p = 19, a = 133, b = 143, then ab = 133 × 143 = 19019, and since this is divisible by 19, the lemma implies that one or both of 133 or 143 must be as well. In fact, 133 = 19 × 7 . The lemma first appeared in Euclid 's Elements , and is a fundamental result in elementary number theory.
As another example, φ(1) = 1 since for n = 1 the only integer in the range from 1 to n is 1 itself, and gcd(1, 1) = 1. Euler's totient function is a multiplicative function , meaning that if two numbers m and n are relatively prime, then φ ( mn ) = φ ( m ) φ ( n ) .
For example, the square of 65 can be calculated by n = 6 × (6 + 1) = 42 which makes the square equal to 4225. If the number is of the form m0 where m represents the preceding digits, its square is n00 where n = m 2. For example, the square of 70 is 4900.
A golden rectangle with long side a + b and short side a can be divided into two pieces: a similar golden rectangle (shaded red, right) with long side a and short side b and a square (shaded blue, left) with sides of length a. This illustrates the relationship a + b / a = a / b = φ.
For example, the ratio one minute : 40 seconds can be reduced by changing the first value to 60 seconds, so the ratio becomes 60 seconds : 40 seconds. Once the units are the same, they can be omitted, and the ratio can be reduced to 3:2. On the other hand, there are non-dimensionless quotients, also known as rates (sometimes also as ratios).
For the multiplicative inverse of a real number, divide 1 by the number. For example, the reciprocal of 5 is one fifth (1/5 or 0.2), and the reciprocal of 0.25 is 1 divided by 0.25, or 4. The reciprocal function, the function f(x) that maps x to 1/x, is one of the simplest examples of a function which is its own inverse (an involution).
The cube of a number n is denoted n 3, using a superscript 3, [a] for example 2 3 = 8. The cube operation can also be defined for any other mathematical expression, for example (x + 1) 3. The cube is also the number multiplied by its square: n 3 = n × n 2 = n × n × n. The cube function is the function x ↦ x 3 (often denoted y = x 3) that ...