Find the linear approximation of the function f(x, y, z) =

x2 + y2 + z2
at (6, 6, 7) and use it to approximate the number

6.012 + 5.972 + 6.982
. (Round your answer to five decimal places.)

f(6.01, 5.97, 6.98) ≈

Respuesta :

Answer:

See below in bold.

Step-by-step explanation:

f(x, y, z) = x^2 + y^2 + z^2 at (6, 6, 7)

Taking partial derivatives

f'x = 2x + y^2 + z^2 --> f'x(6,6,7) =  12+36+49= 97

f'y = x^2 + 2y + z^2---> f'y(6,6,7) = 36 + 12 + 49 = 97

f'z = x^2 + y^2 + 2z ----> f'z(6,6,7) =  36 + 36 + 14 = 86.

f(6,6,7) =  36 + 36 + 49 = 121

So our linear approximation is:

L(x,y,z) = 121 + 97(x - 6) + 97(y - 6) + 86(z - 7)

Substituting the given values

f(6.012, 5.972,6.982)

= L(6.012, 5.972, 6.982) ≈ 121 + 97(6.012 - 6) + 97(5.972 - 6) + 86(6.982 - 7)

= 117.9.

Linear approximation are used to get the approximated values of expressions.

The linear approximation of [tex]\mathbf{f'(6.012, 5.972, 6.982) }[/tex] is 117.90000

The given parameter is;

[tex]\mathbf{f(x, y, z) = x^2 + y^2 + z^2\ at\ (6, 6, 7)}[/tex]

Calculate [tex]\mathbf{f(6, 6, 7)}[/tex]

[tex]\mathbf{f(6, 6, 7) = 6^2 + 6^2 + 7^2}[/tex]

[tex]\mathbf{f(6, 6, 7) = 121}[/tex]

Differentiate (partial derivatives)

[tex]\mathbf{f_x = 2x + y^2 + z^2}[/tex]

[tex]\mathbf{f_y = x^2 + 2y + z^2}[/tex]

[tex]\mathbf{f_z = x^2 + y^2 + 2z}[/tex]

Substitute values for x, y and z in the above partial derivatives

[tex]\mathbf{f_x = 2 \times 6 + 6^2 + 7^2 = 97}[/tex]

[tex]\mathbf{f_y = 6^2 + 2 \times 6 + 7^2 = 97}[/tex]

[tex]\mathbf{f_z = 6^2 + 6^2 + 2 \times 7 = 86}[/tex]

 The linear approximation is calculated as:

[tex]\mathbf{f'(x,y,z) = f(x,y,z) + f_x(x - 6) + f_y(y - 6) + f_z(z - 7)}[/tex]

This gives

[tex]\mathbf{f'(x,y,z) = 121 + 97(x - 6) + 97(y - 6) + 86(z - 7)}[/tex]

Substituting values for x, y and z

[tex]\mathbf{f'(6.012, 5.972, 6.982) \approx 121 + 97 \times (6.012 - 6) + 97\times (5.972 - 6) + 86\times (6.982 - 7)}[/tex]  

[tex]\mathbf{f'(6.012, 5.972, 6.982) \approx 121 + 97 \times .012 + 97 \times -0.028 + 86\times -0.018}[/tex]

[tex]\mathbf{f'(6.012, 5.972, 6.982) \approx 121 + 1.164 -2.716 -1.548 }[/tex]

[tex]\mathbf{f'(6.012, 5.972, 6.982) \approx 117.90000}[/tex]

Hence, the linear approximation of [tex]\mathbf{f'(6.012, 5.972, 6.982) }[/tex] is 117.90000

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