Posted by **Anonymous** on Wednesday, February 18, 2009 at 11:24am.

1. Sketch the curves y=e^x and y=e^-2x, using the same axes. The line y=4 intersects the first curve at A and the second curve at B. Calculate the length AB to two decimal places.

2. Find the coordinates of the turning point on the curve y=2e^3x+8e^-3x and determine the nature of this turning point.

For 1, I have sketched the curves, but i'm not sure how to find the length. I thought I could do y=y to find the x co-ordinates (and use those as my limits) for each but I don't know how to find them out with e^x.

For 2, I differentiated it to get y=6e^3x-24e^-3x and don't know what to do after that.

Please help. Thanks in advance for any help!

- Maths -
**bobpursley**, Wednesday, February 18, 2009 at 12:25pm
2. find each x by

4=e^x

ln 4= x so the point is ln4,4

and the other point is

ln2=-2x

x=-ln4/2 and the boint B is -1/2 ln4,4

Use the distance formula to find the length.

- MATH -
**drwls**, Wednesday, February 18, 2009 at 12:27pm
1. Since the y coordinates of A and B are the same, the distance between the points will be the difference in the X values of those two points.

2. The derivative is

y' = 6e^3x -24e^-3x

When that equals zero,

e^3x = 4e^-3x

e^6x = 4

6x = ln 4 = 1.3863

x = 0.23105 is an extreme point of the function. The value of y there is

2 e^0.693 + 8 e^-0.693 = 2*2 + 8/(1/2) = 20

Take the second derivative of y(x) to see if (0.23105,20) is a minumum or maximum. It is going to be positive. You also see that, since y becomes infinite as x gets much larger, it must be a minimum.

y''(x) =

## Answer this Question

## Related Questions

- calculus - The line y+x=9 intersects the curve y=x^2-2x+3 at the points P and Q...
- Business Statistics - In each case, sketch the two speciﬁed normal curves...
- Statistics - Suppose that the probability distribution of a random variable x ...
- Statistics - Suppose that the probability distribution of a random variable x ...
- Calculus - a) Estimate the area under the graph of f(x)=7+4x^2 from x=-1 to x=2...
- Calc :((((( - The curve y = x/(1 + x^2)is called a serpentine. Find an equation ...
- Calculus - The curve y = x/(1 + x^2) is called a serpentine. Find an equation of...
- Chris - The curve y = x/(1 + x^2) is called a serpentine. Find an equation of ...
- Calc. - sketch the curve using the parametric equation to plot the points. use ...
- calculus - The region A is bounded by the curve y=x^2-5x+6 and the line y = -x...