Which relation is a function? a. {(1, 2), (2, 3), (3,  2), (2, 1)} b. {(4, 2), (3, 3), (2,  4), (3, 2)} c. {(1, −1), (−2, 2), (−1,  2), (1, −2)} d. {(1, 4), (2, 3), (3,  2), (4, 1)}

D

Step-by-step explanation:

A relation is a set of related points. A function is a set of related points where no inputs repeat.

A. {(1, 2), (2, 3), (3,  2), (2, 1)}

This repeats (2,3) and (2,1). Not a function.

​B. {(4, 2), (3, 3), (2,  4), (3, 2)}  

This repeats (3,3) and (3,2). Not a function.

C. {(1, −1), (−2, 2), (−1,  2), (1, −2)}

This repeats (1,-1) and (1,-2). Not a function.

D. {(1, 4), (2, 3), (3,  2), (4, 1)}

This doe NOT repeat. Function.

the distance from any point on the parabola to the focus is the exact same as the distance from that point to the directrix.

if you could provide answer choices that might allow me to answer the question easier if my above answer isn't an option! (:

4444444444444 i think