[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/​mat​h117​5fal​l201​3-​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.