Calculus
posted by Britt .
Minimize S=x+2y with xy=2 and
both x and y > 0.
Can somebody explain to me in words and numbers how to do this problem.

Calculus 
Reiny
First change xy = 2 to y=2/x
then
S = x + 2y
=x + 2(2/x)
= x + 4/x
then S' = 1  4/x^2
= 0 for a max/min of S
solving you get x = ± 2 but x > 0
so x = 2 and y = 2/2 = 1
then S = 2 + 2(1) = 4
Respond to this Question
Similar Questions

drbob222, math ,algebra
can you explain to me the following problem , ms.sue and others are trying to help me but they are making me more confuse. Is there any short cuts to the following problem. Directions:multiply and write the answer in simplest form. … 
Math2(Please help)
Directions:Solve and explain the inequality using words.Tell which wa shading goes. Problem: x+3=>2x+1 and 4x<8 4x<8 The first inequality can be rewritten x <= 2 In words, x is less than or equal to 2. You can get that … 
Calculus
Minimize S=x+2y with xy=2 and both x and y > 0 
Calculus I
Problem: A hot air balloon rising straight up from a level field is tracked by a range finder located 500 feet from the point of liftoff. Express the balloon’s height as a function of the angle the line from the range finder to the … 
calculus
s=4.9t²+245t+14.7 s=4.9(t²245/4.9t)+14.7 s=4.9(t²50t)+14.7 s=4.9(t²50+625625)+14.7 s=4.9(t²50+625)+(4.9)(625)+14.7 s=4.9(t25)²+30625.5+14.17 s=4.9(t25)²+3077.2 as you can see on the process of the problem on … 
Calculus
Calculus Limit Problem: Evaluate the function at the given numbers (correct to six decimal places). Use the results to guess the value of the limit, or explain why it does not exist. f(x)=cosx1/sinx x=1, .5, .4, .3, .2, .1, .05, .01 … 
Algebra ll
X^2  25/2 AND 37/K^2K30 I really need help with these two problems.? 
algebra 2
16t^2 – 1/64 Explain in your own words what the meaning of domain is. Also, explain why a denominator cannot be zero. Find the domain for each of your two rational expressions. Write the domain of each rational expression in set … 
algebra 2
x2 + 2x – 10/ 3x – 15 Explain in your own words what the meaning of domain is. Also, explain why a denominator cannot be zero. Find the domain for each of your two rational expressions. Write the domain of each rational expression … 
calculus 1
Use Newton's method to find all solutions of the equation correct to six decimal places. (Enter your answers as a commaseparated list.) 6 cos(x) = x + 1 can somebody explain to me step by step on how to solve this problem?