00:01
So what we have is the function defined, so it's y equals one over root x, which i would actually rewrite as x to the negative because it's in the denominator and the square root is the 1 1⁄2 power.
00:12
So then when you're asked to find the derivative, you just move the 1 1⁄2 negative 1 1⁄2 in front and you subtract one from the exponent and that's negative 3 1⁄2.
00:24
And if you rewrite that, i just write it with a though because it says where x equals a, then you would write as negative one over two, it's the square root of a cubed.
00:36
That's how you rewrite that problem.
00:38
So then we can find the tangent lines.
00:41
First of all, what's the, well, i guess they tell you it's 1 1, so dy dx at x equals one would be equal to, well, one to any power still one, so it's negative 1 1⁄2.
00:56
So this answer, you might just write it as y minus the y coordinate they tell you is one equals the slope, which is negative 1 1⁄2 and then x minus the x coordinate of one.
01:09
And that should be one of the answers.
01:12
Let me use a different color.
01:14
Dy dx when x equals four...