Posted by **Judy** on Tuesday, September 25, 2007 at 3:04pm.

The point P(4,2) lies on the curve y=x^1/2

If Q is the point (x,x^1/2) use your calculator to find the slope of the secant line PQ for the following values of X:

1)3.5

2)3.9

3)3.99

4)3.999

5)4.5

6)4.1

7)4.01

8)4.001

i plugged these points into the intial equation and got that it was approaching 2. and i made it the slope of secant. however, my friend got a different answer; she found the slope using delta y over delta x. who is right and why?

thanks for any help!

- Calculus -
**drwls**, Tuesday, September 25, 2007 at 6:05pm
4) If the coordinates of Q are

x = 3.999, y = 1.99975

then the slope of the "secant" line between Q and P (4,2) is

(.00025)/.001 = 0.2500 = 1/4

The exact value of the slope of the tangent to the y(x) curve at P is dy/dx = (1/2)/sqrt x = 1/4

For points Q farther from P, you will get a slightly different answer

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