Use the "mixed partials" check to see if the following differential equation is exact.(3x^3 − 3y) dx + (−3x + 2y1) dy = 0
If it is exact find a function F(x,y) whose differential, dF(xy) is the left hand side of the differential equation. That is, level curves F(xy)=C are solutions to the differential equation.

Answer:

good point I don't know that either

Step-by-step explanation:

−2x+5y=−15 and 5x+2y=−6

Rewrite equations:

−2x+5y=−15;5x+2y=−6

Step: Solve−2x+5y=−15for x:

−2x+5y=−15

−2x+5y+−5y=−15+−5y(Add -5y to both sides)

−2x=−5y−15

−2x−2=−5y−15−2(Divide both sides by -2)

x=52y+152

Step: Substitute52y+152forxin5x+2y=−6:

5x+2y=−6

5(52y+152)+2y=−6

292y+752=−6(Simplify both sides of the equation)

292y+752+−752=−6+−752(Add (-75)/2 to both sides)

292y=−872

292y292=−872292(Divide both sides by 29/2)

y=−3

Step: Substitute−3foryinx=52y+152:

x=52y+152

x=52(−3)+152

x=0(Simplify both sides of the equation)

Answer:

x=0 and y=−3

Answer:

The maximum volume of such box is 32m^3

V = x×y×z = 32 m^3

Step-by-step explanation:

Given;

Total surface area S = 48m^2

Volume of a rectangular box V = length×width×height

V = xyz ......1

Total surface area of a rectangular box without a lid is

S = xy + 2xz + 2yz = 48 .....2

To be able to maximize the volume, we need to reduce the number of variables.

Let assume the rectangular box has a square base,that means; length = width

x = y

Substituting y with x in equation 1 and 2;

V = x^2(z) ....3

x^2 + 4xz = 48 .....4

Making z the subject of formula in equation 4

4xz = 48 - x^2

z = (48 - x^2)/4x .......5

To be able to maximize V, we need to reduce the number of variables to 1, by substituting equation 5 into equation 3

V = x^2 × (48 - x^2)/4x

V = (48x - x^3)/4

differentiating V with respect to x;

V' = (48 - 3x^2)/4

At the maximum point V' = 0

V' = (48 - 3x^2)/4 = 0

Solving for x;

3x^2 = 48

x = √(48/3)

x = √(16)

x = 4

Since x = y

y = 4

From equation 5;

z = (48 - x^2)/4x

z = (48 - 4^2)/4(4)

z = 32/16

z = 2

The maximum volume can be derived by substituting x,y,z into equation 1;

V = xyz = 4×4×2 = 32 m^3

Answer:

Step-by-step explanation:

x=-12

Answer:

x= -12

Step-by-step explanation: