The answer for your question is a
        
                    
             
        
        
        
1. Commutative property of multiplication This is because it represents a*b=b*a
2. Associative property of multiplication. Multiplication problems end with the same product no matter the order of factors.
3. Correct
4. Correct
5. Associative property of addition. Even though the grouping symbols are different, it is equivalent because you are adding all the terms together.
6. Correct
The last one should also be associative property since it applies every time you combine like terms.
Just a reminder: Distributive property is only when you multiply in the form of a(b+c)=ab+ac
        
             
        
        
        
By inspection, it's clear that the sequence must converge to 

 because

when 

 is arbitrarily large.
Now, for the limit as 

 to be equal to 

 is to say that for any 

, there exists some 

 such that whenever 

, it follows that

From this inequality, we get




As we're considering 

, we can omit the first inequality.
We can then see that choosing 

 will guarantee the condition for the limit to exist. We take the ceiling (least integer larger than the given bound) just so that 

.
 
        
        
        
Since a^2+b^2=c^2 becomes 20^2+b^2=29^2, we solve for b:
400+b^2=841
b^2=441
b=21
So the length of b is 21 units.
Hope this helped!