Answer: The Max fun is 9, and the Min fun is -3
Step-by-step explanation:
Please follow the steps carefully;
Let us consider the function f(x,y) = xy -------------- (1)
We will apply the Lagrange multipliers to maximize the function f(x,y) subject to the constraint g(x,y) = x^2+y^2-xy = 9
By differentiating (1) w.r.t x, we get fx(x,y) = y
By differentiating (1) w.r.t y, we get fy(x,y) = x
By differentiating g(x,y) w.r.t x, we get gx(x,y) = 2x - y
Also By differentiating g(x,y) w.r.t y, we get gy(x,y) = 2y - x
let us take
fx = λgx
where y = λ(2x - y)
y/2x - y = λ ----------- (2)
fy = λgy
where x = λ(2y - x)
λ = x/2y -x ----------- (2)
Let us equate (2) and (3)
y/2x - y = x/2y -x
2y² - xy = 2x² - xy
2y² = 2x² after cancelling like terms
y² = x²
So y = ±x
Now let us substitute y = x into the given constraint
x² + y² - xy = 9
x² + x² - x(x) = 9
x² = 9
therefore x = ± 3
We can conclude that when x = ±3, ⇒ y = ±3
The corresponding points are (3,3), (-3,-3)
Substitue y = -x in the given constraint gives
x² + y² - xy = 9
x² + (-x)² -x(-x) = 9
3x² = 9
x² = 3
x = ±√3
The corresponding points are (√3,-√3), (-√3,√3)
The function value is
f(x,y) = xy
f (√3,-√3) = (√3)(-√3) = -3
f (-√3,√3) = (-√3)(√3) = -3
we get;
f(3,3) = (3)(3) = 9
and
f (-3,-3) = (-3)(-3) = 9
We can conclusively say that ;
The Maximum value of the function is 9
The Minimum value of the function is -3
cheers i hope this helped
