[Suman Ganguli]

Hi,

I put up a post about HW#1 as well as some links to relevant Khan Academy videos:
http://openlab.citytech.cuny.edu/math1175fall2013-ganguli/2013/09/13/ch-2-linear-equations-recap-hw-1/

Hopefully you’ll all been able to log in to WebWork (http://mathww.citytech.cuny.edu/webwork2/MAT1175-Ganguli/). As I said in class, your username is your first initial followed by your last name, and your initial password is the same as your username.

I encourage you to use WebWork, but you can also choose to do homework exercises from the textbook. I’ve listed the WebWork sets or textbook exercises to do for HW#1 in the link above.

Let me know if you have any questions.

-Suman

[Suman Ganguli]

I got questions about a couple of the WebWork exercises:

For exercises where the slope of a line is undefined (i.e., a vertical line) and you’re asked to enter the slope, you can enter “does not exist”

For LinesEquation Problems 2 and 3, there’s a small typo: even though there is already a “y=” to the left of the box where you’re asked to enter the equation of the line in slope-intercept form, it seems like you have to enter the entire equation into the box for these exercises, i.e., retype “y = ” in the box.

Hope that helps. Let me know if you come across any other issues as you work through these homework sets.

[Suman Ganguli]

I also got a question about the last 3 problems on the LinesEquation WebWork set, which deal with applications of linear equations. In each case

For #18, think of T as the y-variable and d as the x-variable. Since the given temperature of the soil at the surfaceis the value of T when d=0, i.e., the T-intercept which is the value of b in the equation T = md + b that you want to find. The other given piece of information, the rate at which the temperature decreases for each centimeter below the surface, gives you the slope–for each “run” of d=1cm, you have a given “rise” in T (actually a decrease in T, meaning the slope is negative).

Now you can write the equation for T in terms of d in slope-intercept form.

#19 and #20 are similar.

For #19, “the distance from home D” is the y-variable, and “the number of days d” is the x-variable. You’re told that the distance the pigeon starts from home–that’s the value of d-intercept, i.e., the value of D when d=0. The other piece of information gives you the slope–the rate at which the pigeon flies home every day (the change in D for a change in d of 1).

For #19, the height h is the y-variable and the time since purchase t is the x-variable.