Let f(x)=5x^2-4x and g(x)=5x+1. find f-g

D.a relation only

Step-by-step explanation:

Relation: It is mapping between two non empty set A and B.

In relation any input value can have two or more than two output values.

Function: It is that relation in which every input value has only one output .

All function are relations but all relations are not function.

In given data

Image of 3 =4

Image of 3=3

By definition of function

It is not a function.

By definition of relation

It is a relation.

Hence, option D is true.