Answer:
ST = 7.07 units
Step-by-step explanation:
* Lets explain how to find the length of a segment
- The length of a segment whose endpoints are 
and
can be founded by the rule of the distance

* Lets solve the problem
∵ The line segment is ST
∵ S is (-3 , 10)
∵ T is (-2 , 3)
- Assume that S is
and T is 
∴
and 
∴
and 
- By using the rule above
∴ 
∴ 
∴ 
∴ 
∴ ST = 7.07 units
Plug in n = 1 into the nth term formula
a(n) = 4n-1
a(1) = 4*1-1
a(1) = 3
So the first term is 3
The second term will be 7 because we add on 4 each time, as indicated by the slope of 4. This is also known as the common difference.
So the nth term is found by adding 4 to the (n-1)st term, in other words,
a(n) = a(n-1)+4
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In summary, the answer is
a1=3; an=an-1+4
which is choice B
If you complete the square you get

and as any number squared is positive and 4 is positive, the result must be positive