00:01
Here we're given the equation f of x, which is equal to 4 times a square root of x, and we're given at the point x equals 9.
00:09
And we want to find the y intercept of the tangent line.
00:13
Now to do that, let's just find the y intercept, or sorry the tangent line, and then we'll know the y intercept.
00:18
So what i'm going to do is find y equals y0 plus m times x minus x9.
00:26
So the first thing to note is we already know x not, that's 9.
00:29
This is the value we're given.
00:31
So what's why not? well, why not is about what happens if i plug that in? so what is 4 times the square root of 9? that's 4 times 3, which is 12.
00:40
So the y value at 9 is 3.
00:43
So that means why not is 3.
00:47
So now all we have to do is what is the slope at that point? by definition, that means the slope of the tangent line...