53x2=106
250-106= 144
144/2=72
The length is 72cm
Answer:

Step-by-step explanation:
By definition, we can write ln instead of log. WHEN??
Whenever the base of the logarithm is the number "e".
Hence, when we have:

We can write it in shortcut as:

Hence, ln x can also be written as 
Fourth answer choice is right.
Answer:
D. 21.
Step-by-step explanation:
The general form of the equation of a circle is:
(x - a)^2 + (y - b)^2 = r^2 where r is the radius.
Comparing:
(x + 5)^2 + (y + 7)^2 = 21^2
So r^2 = 21^2
making r = √21^2
= 21.
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