Answer:

Step-by-step explanation:
The LCM of 14, 21 and 6 is 42
We require to change the fractions to fractions with a denominator of 42
+
+ 
=
+
+
← add the numerators, leaving the denominator
= 
=
← divide both values by 2
=
← in simplest form
Its B.. Hope that helps :)
(A)
Choice (B) is not the right answer because I
it's only 3rd order. But because f(x) goes to negative infinity when x goes to positive infinity means that the right answer is (A).
here is the process hope it helps you