+0  
 
0
92
2
avatar

Let x and y be real numbers such that 2(x^2 + y^2) = x + y + 8.  Find the maximum value of x - y.

 May 22, 2021
 #1
avatar
0

The maximum value of x - y is 3*sqrt(2).

 May 22, 2021
 #2
avatar
0

The above is the graph of

I used Winplot to plot the two functions and find their extreme values. You could also use calculus to do the same , and if requested, I would be happy to show my work.

But where does the equation come from? The equation given is the equation of a circle that has the standard form

 

I solved this equation for y to get

and then subtracted the expression for y from x to get f(x). By the way, the exact values of the coordinates of the extreme point displayed in the plot are

So the maximum value of x-y is \(\frac{\sqrt{33}}{2}\) or approximately 2.87228.

 May 23, 2021

45 Online Users

avatar