Calculus Help??

Test Preparation
1

<p>I’m so frustrated right now! I can’t do these simple problems from my calculus book without getting the wrong answers!</p>

<li><p>(Directions are: Find two postive numbers that satisfy the given requirements) The second number is the reciprocal of the first and the sum is a minimum.</p></li>
<li><p>(Directions are: Find the length and width of a rectangle that has the given permeter and a maximum area) Perimeter: P units</p></li>
</ol>

2

<p>a1=1/a2
d/da1(a1+a2)=d/da1(a1+1/a1)
1-a1^-2=0(minimum)
a1=1 use the sign chart to confirm that a1=1 is the minimum.</p>

3

<p>x,y
4(x+y)=k(given value) x=(k-4y)/4
xy=(k-4y)/4<em>y
d/dy(k-4y)/4</em>y
find the derivative and confirm that the critical point is a maximum</p>

4

<p>Thanks so much! :)</p>

5

<p>oh sorry it's 2(x+y) not 4(x+y)</p>