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Use Lagrange multipliers to find the points on the given surface y^(2)=16+xz that are closest to the origin.
{:[" (smaller "y"-value) ",(x","y","z)=(◻)],[" (larger "y"-value) ",(x","y","z)=(◻)]:}

Use Lagrange multipliers to find the points on the given surface y2=16+xz y^{2}=16+x z that are closest to the origin.\newline (smaller y-value) amp;(x,y,z)=() (larger y-value) amp;(x,y,z)=() \begin{array}{ll} \text { (smaller } y \text {-value) } & (x, y, z)=(\square) \\ \text { (larger } y \text {-value) } & (x, y, z)=(\square) \end{array}

Full solution

Q. Use Lagrange multipliers to find the points on the given surface y2=16+xz y^{2}=16+x z that are closest to the origin.\newline (smaller y-value) (x,y,z)=() (larger y-value) (x,y,z)=() \begin{array}{ll} \text { (smaller } y \text {-value) } & (x, y, z)=(\square) \\ \text { (larger } y \text {-value) } & (x, y, z)=(\square) \end{array}
  1. Define Objective Function: Define the objective function and the constraint.\newlineThe objective function to minimize is the distance squared from the origin, which is D(x,y,z)=x2+y2+z2D(x, y, z) = x^2 + y^2 + z^2. We square the distance to avoid dealing with square roots, which simplifies the calculus without affecting the location of the minimum. The constraint is given by the equation of the surface, G(x,y,z)=y216xz=0G(x, y, z) = y^2 - 16 - xz = 0.
  2. Set Up Equations: Set up the system of equations using Lagrange multipliers.\newlineTo find the points closest to the origin, we use the method of Lagrange multipliers. This involves setting the gradient of the objective function equal to a constant (the Lagrange multiplier, λ\lambda) times the gradient of the constraint:\newline\(\newlineabla D(x, y, z) = \lambda\newlineabla G(x, y, z)\)\newlineThis gives us the following system of equations:\newline11) 2x=λ(z)2x = \lambda(-z) (derivative of DD with respect to xx equals λ\lambda times derivative of GG with respect to xx)\newline22) 2y=λ(2y)2y = \lambda(2y) (derivative of DD with respect to \(\newlineabla D(x, y, z) = \lambda\newlineabla G(x, y, z)\)00 equals λ\lambda times derivative of GG with respect to \(\newlineabla D(x, y, z) = \lambda\newlineabla G(x, y, z)\)00)\newline33) \(\newlineabla D(x, y, z) = \lambda\newlineabla G(x, y, z)\)44 (derivative of DD with respect to \(\newlineabla D(x, y, z) = \lambda\newlineabla G(x, y, z)\)66 equals λ\lambda times derivative of GG with respect to \(\newlineabla D(x, y, z) = \lambda\newlineabla G(x, y, z)\)66)\newline44) 2x=λ(z)2x = \lambda(-z)00 (the original constraint)
  3. Solve Equations: Solve the system of equations.\newlineFrom equation 11) and 33), we can see that if λ\lambda is not zero, then x=zx = -z and z=xz = -x, which implies x=zx = z. Substituting xx for zz in the constraint equation 44) gives us y2=16+x2y^2 = 16 + x^2. Now we can solve for xx in terms of yy using this equation.
  4. Find Relationship: Find the relationship between xx and yy. Substituting x=zx = z into y2=16+xzy^2 = 16 + xz, we get y2=16+x2y^2 = 16 + x^2. Rearranging, we have x2=y216x^2 = y^2 - 16. Since x=zx = z, we also have z2=y216z^2 = y^2 - 16.
  5. Analyze Data: Analyze the relationship between xx, yy, and zz. From equation 22), we have 2y=λ(2y)2y = \lambda(2y). If λ\lambda is not 11, then yy must be 00. However, if y=0y = 0, then the constraint equation becomes yy00, which is not possible since yy11. Therefore, λ\lambda must be 11, and we do not get any additional information about yy from this equation.
  6. Substitute xx: Substitute x=zx = z into the distance function.\newlineSince x=zx = z, the distance function D(x,y,z)=x2+y2+z2D(x, y, z) = x^2 + y^2 + z^2 becomes D(x,y,x)=2x2+y2D(x, y, x) = 2x^2 + y^2. We already have x2=y216x^2 = y^2 - 16 from Step 44, so we can substitute this into the distance function to get D(y)=2(y216)+y2=3y232D(y) = 2(y^2 - 16) + y^2 = 3y^2 - 32.
  7. Minimize Distance: Minimize the distance function D(y)D(y) with respect to yy. To find the minimum distance, we take the derivative of D(y)D(y) with respect to yy and set it equal to zero:\newlinedDdy=6y=0\frac{dD}{dy} = 6y = 0\newlineThis implies that y=0y = 0, which contradicts our earlier finding that yy cannot be zero. This indicates a mistake has been made in the previous steps.

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