LetX1={5,10,15,20}andY1={5,10,15,20 ,25}. Using the formal definition of a func-tion, determine which of the following subsets ofX1×Y1correspond to the functions ofX1→Y1.
Justifyyour answer by providing reasons why each is or is not a function.
a) 1(a)f={(5,20),(10,15),(5,10),(15,5) ,(20,5)}
b) 1(b)f={(5,25),(10,5),(15,5),(20,10) ,(5,25)}
c) 1(c)f={(5,5),(10,5),(15,5)}

Option b) is the answer

Step-by-step explanation:

A function from X₁ to Y₁ is an object f such that every x in X₁ is uniquely associated with an object f(x) = y in Y₁.

Then

1(b)f={(5,25),(10,5),(15,5),(20,10),(5,25)} is the correct answer.

It follows that

f(5) = 25

f(10) = 5

f(15) = 5

f(20) = 10

c

step-by-step explanation:

15

step-by-step explanation:

we are given the following expression and we are to solve it and find the product:

-13 × (-5)

solving the given expression in the standard order of solving a mathematical expression, beginning with the opening of brackets and then multiplying the terms and changing their signs.

-3 × -5 = 15 (answer is positive because when negative is multiplied with negative, it gives a positive answer)