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RoseWind [281]
4 years ago
8

PLZ help with expression

Mathematics
1 answer:
umka2103 [35]4 years ago
6 0
The last two options are correct, but it looks like you’ve got them :)
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The plane x+y+2z=8 intersects the paraboloid z=x2+y2 in an ellipse. Find the points on this ellipse that are nearest to and fart
DiKsa [7]

Answer:

The minimum distance of   √((195-19√33)/8)  occurs at  ((-1+√33)/4; (-1+√33)/4; (17-√33)/4)  and the maximum distance of  √((195+19√33)/8)  occurs at (-(1+√33)/4; - (1+√33)/4; (17+√33)/4)

Step-by-step explanation:

Here, the two constraints are

g (x, y, z) = x + y + 2z − 8  

and  

h (x, y, z) = x ² + y² − z.

Any critical  point that we find during the Lagrange multiplier process will satisfy both of these constraints, so we  actually don’t need to find an explicit equation for the ellipse that is their intersection.

Suppose that (x, y, z) is any point that satisfies both of the constraints (and hence is on the ellipse.)

Then the distance from (x, y, z) to the origin is given by

√((x − 0)² + (y − 0)² + (z − 0)² ).

This expression (and its partial derivatives) would be cumbersome to work with, so we will find the the extrema  of the square of the distance. Thus, our objective function is

f(x, y, z) = x ² + y ² + z ²

and

∇f = (2x, 2y, 2z )

λ∇g = (λ, λ, 2λ)

µ∇h = (2µx, 2µy, −µ)

Thus the system we need to solve for (x, y, z) is

                           2x = λ + 2µx                         (1)

                           2y = λ + 2µy                       (2)

                           2z = 2λ − µ                          (3)

                           x + y + 2z = 8                      (4)

                           x ² + y ² − z = 0                     (5)

Subtracting (2) from (1) and factoring gives

                     2 (x − y) = 2µ (x − y)

so µ = 1  whenever x ≠ y. Substituting µ = 1 into (1) gives us λ = 0 and substituting µ = 1 and λ = 0  into (3) gives us  2z = −1  and thus z = − 1 /2 . Subtituting z = − 1 /2  into (4) and (5) gives us

                            x + y − 9 = 0

                         x ² + y ² +  1 /2  = 0

however, x ² + y ² +  1 /2  = 0  has no solution. Thus we must have x = y.

Since we now know x = y, (4) and (5) become

2x + 2z = 8

2x  ² − z = 0

so

z = 4 − x

z = 2x²

Combining these together gives us  2x²  = 4 − x , so

2x²  + x − 4 = 0 which has solutions

x =  (-1+√33)/4

and

x = -(1+√33)/4.

Further substitution yeilds the critical points  

((-1+√33)/4; (-1+√33)/4; (17-√33)/4)   and

(-(1+√33)/4; - (1+√33)/4; (17+√33)/4).

Substituting these into our  objective function gives us

f((-1+√33)/4; (-1+√33)/4; (17-√33)/4) = (195-19√33)/8

f(-(1+√33)/4; - (1+√33)/4; (17+√33)/4) = (195+19√33)/8

Thus minimum distance of   √((195-19√33)/8)  occurs at  ((-1+√33)/4; (-1+√33)/4; (17-√33)/4)  and the maximum distance of  √((195+19√33)/8)  occurs at (-(1+√33)/4; - (1+√33)/4; (17+√33)/4)

4 0
3 years ago
A motorboat covers the distance from one pier to the other pier in 4 hours and the way back in 5 hours. What is the speed of the
aleksklad [387]
R = speed in still water
r + c = speed with current
r - c = speed against current

3.5(r + c) = 70
r + c = 20
c = 20 - r

4(r + c) = distance from pier to pier
5(r - c) = distance from pier to pier
4(r + c) = 5(r - c)
4(r + 20 - r) = 5(r - 20 + r)
80 = 10r - 100
180 = 10r
18 = r
The speed in still water is 18 km/hour
3 0
3 years ago
In order to conduct an experiment five subjects are randomly selected from a group of 48 subjects how many different groups of f
exis [7]

Answer:

1,712,304 ways

Step-by-step explanation:

This problem bothers on combination

Since we are to select 5 subjects from a pool of 48 subjects, the number of ways this can be done is expressed as;

48C5 = 48!/(48-5)!5!

48C5 = 48!/43!5!

48C5 = 48×47×46×45×44×43!/43!5!

48C5 = 48×47×46×45×44/5!

48C5 = 205,476,480/120

48C5 = 1,712,304

Hence this can be done in 1,712,304ways

3 0
3 years ago
Ui5<br> -4<br> Solve each equation.<br> 1) 2a - 8a = 12 - 8a
vredina [299]

Answer:

Sorry, I forgot what the a means

Step-by-step explanation:

is it multiplcation , division, subtraction, or addition?

3 0
3 years ago
What is the area, in square inches, of the trapezoid below?
Anastaziya [24]

Answer: 88.8in^2

Step-by-step explanation:

4 0
3 years ago
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