Math Problem Statement

g(x,y)=(10-xy)^0.5 find g sub x and sub y and then calculate them on (1.5,3.5)

Solution

We are given the function g(x,y)=10xyg(x, y) = \sqrt{10 - xy}. Our task is to find the partial derivatives of gg with respect to xx and yy, and then evaluate them at the point (x,y)=(1.5,3.5)(x, y) = (1.5, 3.5).

Step 1: Compute the partial derivative of g(x,y)g(x, y) with respect to xx

The function is g(x,y)=10xyg(x, y) = \sqrt{10 - xy}, so we use the chain rule to differentiate with respect to xx.

gx=x(10xy)=1210xy(y)g_x = \frac{\partial}{\partial x} \left( \sqrt{10 - xy} \right) = \frac{1}{2 \sqrt{10 - xy}} \cdot (-y)

So,

gx=y210xyg_x = \frac{-y}{2 \sqrt{10 - xy}}

Step 2: Compute the partial derivative of g(x,y)g(x, y) with respect to yy

Now, we differentiate g(x,y)g(x, y) with respect to yy, again using the chain rule:

gy=y(10xy)=1210xy(x)g_y = \frac{\partial}{\partial y} \left( \sqrt{10 - xy} \right) = \frac{1}{2 \sqrt{10 - xy}} \cdot (-x)

So,

gy=x210xyg_y = \frac{-x}{2 \sqrt{10 - xy}}

Step 3: Evaluate gxg_x and gyg_y at (x,y)=(1.5,3.5)(x, y) = (1.5, 3.5)

Now, we substitute x=1.5x = 1.5 and y=3.5y = 3.5 into the expressions for gxg_x and gyg_y.

First, calculate 10xy10 - xy at (x,y)=(1.5,3.5)(x, y) = (1.5, 3.5):

101.5×3.5=105.25=4.7510 - 1.5 \times 3.5 = 10 - 5.25 = 4.75

Thus,

101.5×3.5=4.752.179\sqrt{10 - 1.5 \times 3.5} = \sqrt{4.75} \approx 2.179

Now calculate gxg_x and gyg_y:

gx=3.52×2.179=3.54.3580.803g_x = \frac{-3.5}{2 \times 2.179} = \frac{-3.5}{4.358} \approx -0.803

gy=1.52×2.179=1.54.3580.344g_y = \frac{-1.5}{2 \times 2.179} = \frac{-1.5}{4.358} \approx -0.344

Final Results:

  • gx(1.5,3.5)0.803g_x(1.5, 3.5) \approx -0.803
  • gy(1.5,3.5)0.344g_y(1.5, 3.5) \approx -0.344

Would you like further details or clarifications on any step?

Here are some related questions:

  1. How would the partial derivatives change if the function were g(x,y)=x2+y2g(x, y) = \sqrt{x^2 + y^2}?
  2. Can you explain how to apply the chain rule in partial derivatives?
  3. What is the geometric interpretation of partial derivatives in multivariable calculus?
  4. How do you compute second-order partial derivatives like gxxg_{xx} or gxyg_{xy}?
  5. How do you evaluate partial derivatives at boundary points or singularities?

Tip: When differentiating a function of multiple variables, always remember to treat the other variables as constants when taking partial derivatives.

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Math Problem Analysis

Mathematical Concepts

Multivariable Calculus
Partial Derivatives
Chain Rule

Formulas

g_x = (-y) / (2 * sqrt(10 - xy))
g_y = (-x) / (2 * sqrt(10 - xy))
sqrt(10 - xy)

Theorems

Chain Rule for Partial Derivatives

Suitable Grade Level

College-Level Calculus