The first order approximation of f(x,y) around some point (a,b) is:

$$f(x,y) = f(a,b) + f_x(a,b) (x-a) + f_y(a,b) (y-b)$$

In your case:

$$f(x,y) = f(-9,9) + f_x(-9,9) (x - -9) + f_y(-9,9) (y - 9)$$

Fill in your values to get the results...

reinout-g: Thank you I like Serena ,I tried what you did and this is what I got;I had to add the extra variables u_{1} and u_{2} since otherwise I could not eliminate the top row (maybe there was an easier way to do that).My slack variables saved me by directly giving me my u_{1} and u_{2} values.Thanks again,truly appreciated Reinout

Thank you I like Serena ,I tried what you did and this is what I got;I had to add the extra variables u_{1} and u_{2} since otherwise I could not eliminate the top row (maybe there was an easier way to do that).My slack variables saved me by directly giving me my u_{1} and u_{2} values.Thanks again,truly appreciated Reinout

Jedithious: Hello, I was wondering if anyone knows of any apps that can graph such things as ellipses, circles, and hyperbolas? I certainly have a few apps in which you can enter a function and get a graph for it, but what about being able to input such things as the focus, directrix, and endpoints in order to come up with conic sections?Thanks

Hello, I was wondering if anyone knows of any apps that can graph such things as ellipses, circles, and hyperbolas? I certainly have a few apps in which you can enter a function and get a graph for it, but what about being able to input such things as the focus, directrix, and endpoints in order to come up with conic sections?Thanks

reinout-g: I had an exam yesterday of the class 'introduction to operations research' and one of the questions was the following;Now I don't know whether there is anyone at this forum with knowledge of the simplex method, but I'm still wondering how this question can be done.

I had an exam yesterday of the class 'introduction to operations research' and one of the questions was the following;Now I don't know whether there is anyone at this forum with knowledge of the simplex method, but I'm still wondering how this question can be done.

reinout-g: Almost had it

Almost had it

kateeelllyyynn: 99% CI for the population proportion of voters opposing a new tax was calculated to be (.68,.76). What was the sample proportion of voters who oppose the new tax

99% CI for the population proportion of voters opposing a new tax was calculated to be (.68,.76). What was the sample proportion of voters who oppose the new tax

Princess Sophie E: The electrostatic force between two charges Q1 and Q2 at a distance r apart is given by F=(Q1*Q2)/(4Pie*Eo*r^2). What is the unit of E?

The electrostatic force between two charges Q1 and Q2 at a distance r apart is given by F=(Q1*Q2)/(4Pie*Eo*r^2). What is the unit of E?

kat:}: :| [size=150]a wheelbarrow can carry up to 300 pounds of weight. A bag of soil weighs 20 pounds. write and solve an inequality to represent the number of bags of soil the wheelbarrow can carry.[/size]

:| [size=150]a wheelbarrow can carry up to 300 pounds of weight. A bag of soil weighs 20 pounds. write and solve an inequality to represent the number of bags of soil the wheelbarrow can carry.[/size]

Irreverent Statistic: What is the probability that "I like Serena" will make a comment on a question that either states the obvious or is trivial and useless.

What is the probability that "I like Serena" will make a comment on a question that either states the obvious or is trivial and useless.

personunknown: The mass of a single rhodium atom is 1.71E-22 grams. How many rhodium atoms would there be in 238 milligrams of rhodium?

The mass of a single rhodium atom is 1.71E-22 grams. How many rhodium atoms would there be in 238 milligrams of rhodium?

Melody: All questions answered EXCEPT a T-test ?

All questions answered EXCEPT a T-test ?