00:01
Today we'll be finding the equation of a line change into the curve y equals 5x over 1 plus x squared at the point 2 .2 to do this we'll start by finding the slope, which means we have to find the derivative.
00:12
So y prime equals with the quotient rule, as i learned it we have the bottom 1 plus x squared times the derivative of the top which is 5 minus the top which is 5x times the derivative of the bottom which is 2x all divided by the bottom of the bottom squared.
00:31
So 1 plus x squared squared.
00:35
So we'll plug two in for x since that is our x value, and we will have 1 plus 2 squared times 5 minus 5 times 2 times 2 times 2.
00:51
I'll rewrite this, times 2 all over 1 plus 2 squared squared.
01:01
So we'll simplify that.
01:04
That will be 5.
01:06
Times 5 minus 10 times 4 over 5 squared, which is 25 minus 40 over 25.
01:20
And 25 minus 40 is 15, well, negative 15.
01:25
So negative 15 over 25, which when you reduce it, gives us negative 3 over 5 as our slope.
01:33
So then, to find the equation of a line, it's y minus y 0 equals m, times x minus x 0 and x 0 y 0 we're given to us as 2 2.
01:47
So just to plug in, we have y minus 2 equals negative 3 5ths times x minus 2.
02:01
We'll explain that and solve for y.
02:04
So y equals negative 3 5ths plus 6, 10 5ths...