Answer:
20 but I am not sure.....

Differentiate both sides, treating
as a function of
. Let's take it one term at a time.
Power, product and chain rules:



Product and chain rules:




Product and chain rules:




The derivative of 0 is, of course, 0. So we have, upon differentiating everything,

Isolate the derivative, and solve for it:


(See comment below; all the 6s should be 2s)
We can simplify this a bit by multiplying the numerator and denominator by
to get rid of that fraction in the denominator.

We want to use elimination to solve
y = 0 (1)
x + y = 40 (2)
Multiply (1) by -1 to eliminate y.
-y = 0 (3)
Add (2) and (3).
x + y + (-y) = 40 + 0
x = 40
Answer: Multiply by -1.
Answer:
The expression is not defined in a set of real numbers.
The square root of a negative number is not defined in the set of real numbers.
7.7 the answer in 7.7 because 2+5 = 7 and 3+4= 11