Answer:
 81
Step-by-step explanation:
from 4 to 5,the difference is 1 ,and when you multiply by 3, then add 3 to 5 ,it gives you 8 ,to get 17,I multiple 3by 3 and add the answer to 8 ,and the same continues upto when you get the final answer which is 81.
difference is just multiplying the previous difference with 3 and add it with the previous number . 
 
        
             
        
        
        
Answer:
and the addition will be p+q
Step-by-step explanation:
the diffrence between p and q is u have to add so the answer will be p-q
 
        
             
        
        
        
The second answer i think is the best one
        
                    
             
        
        
        
Answer:
Answer C
Step-by-step explanation:
Give brainliest
 
        
                    
             
        
        
        
Answer:
not a right triangle
Step-by-step explanation:
We can use the Pythagorean theorem to see if it is a right triangle
a^2 + b^2 = c^2
15^2 + 12^2 = 21^2
225 + 144 = 441
369 = 441
This is not true so it is not a right triangle