00:01
Hi, let's start the solution.
00:02
In this question we have given function fx ,y is xy -2y -4x8 ,y equal to x square ,y equal to 5.
00:16
So for critical points differentiate function with respect to x, fx is this one is y -4 that is equal to 0, so we get here y equal to 4.
00:32
Now f of y that is x -2 equal to 0, so we get here x equal to 2.
00:42
So we get x ,y that is equal to 2 ,4 lies in the given region described by y equal to x square, y equal to 5.
01:07
So f 2 ,4 that is equal to 2 into 4 minus 2 into 4 minus 4 into 2 plus 8.
01:19
So by simplifying this here we get f 2 ,4 equal to 0.
01:26
Now f x ,y is xy -2y -4x plus 8 and y equal to x square.
01:37
So put y equal to x square here, we get f of x equal to x into x, x into x square is x cube minus 2x square minus 4x plus 8.
01:50
So for critical points differentiate f of x with respect to x, we get df upon dx that is 3x square minus 6x minus 4 and this one is 2 2's of 4 that is 4x.
02:11
Now put df upon dx equal to 0, so we get 3x square minus 4x minus 4 equal to 0.
02:19
Now by using the quadratic formula here we find the roots that is 3x plus 2 into x minus 2 equal to 0.
02:29
So we get here x equal to minus 2 by 3 and x equal to 2...