The correct answer is p/rs.
In order to find this first state the direct variation with the constant k included.
p = krs
Now to find the value of k, we simply divide away the r and s
p/rs = k
By first principles, the derivative is
Use the binomial theorem to expand the numerator:
where
The first term is eliminated, and the limit is
A power of 
in every term of the numerator cancels with in the denominator:
Finally, each term containing approaches 0 as 
, and the derivative is
Answer:
Step-by-step explanation:
1. 10² + 7² = x²
149 = x²
x = √149
2. x² + 19² = 21²
x² = 21² - 19² = 80
x = √80 = 4√5
3. x² + 16² = 27²
x² = 27² - 16² = 473
x = √473
4. 5.3² + 12.8² = x²
191.93 = x²
x = √191.93
5. 9² + 20² = x²
481 = x²
x = √481
6. 31 = x + 2√(19²-17²) = x + 2·6√2 = x + 12√2
x = 31 - 12√2
