You forgot to post the function
I’m not sure just need to answer questions to help me so sorry
Given that triangle ABC is right angle triangle. CD is altitude such that AD=BC
ABC is a right angle triangle so apply Pythogorean theorem

(Given that AD = BC)
(Given that AB=3)
...(i)
ADC is a right angle triangle so apply Pythogorean theorem



...(ii)
Plug value (ii) into (i)





Hence final answer is 
14) The sum of anything and its additive inverse is zero. (That is the definition of additive inverse.) The appropriate choice is ...
... A) equal to 0