2008 Second Semester MATHS课程问答帖(请用英文提问)

ycho126

thx so much!!

however, i got another problem which is.....
Use the formal definition of differentiation as a limit to find the derivative f'(x).  where f(x) = 1/(x-1).
I know the ans is -1/(x-1)^2, but i can't get the answer by using "formal definition"......

萨米

原帖由 ycho126 于 2008-5-16 15:51 发表
so do u mean i just randomly choose a real number to let det(A) not equal to 0?
for example, det(A) = 2

Make it to REF and determine the det.

ycho126

so do u mean i just randomly choose a real number to let det(A) not equal to 0?
for example, det(A) = 2

萨米

原帖由 ycho126 于 2008-5-15 18:05 发表
Q3
Find the values of k for which the matrix A = [1 -1 -2 ; 3 k k ; 3 1 k] is invertible.

can i have some hints of how to do this question please?? thx so much

Only the determinent is not 0.

ycho126

Q3
Find the values of k for which the matrix A = [1 -1 -2 ; 3 k k ; 3 1 k] is invertible.

can i have some hints of how to do this question please?? thx so much

jennyyang

q8 Assign 2

suppose P and Q are two distinct planes in R^3. what sort of set could their intersection be? answer in words and give a sketch to show the possibilities.

jennyyang

Maths 108, ASSIGN 2, Question 8
Could you please explain to me how should I do this question? Its confusing

花花花狸鼠

consider the system of linear equatoins,
x+y+kz = 2
3x+4y+2z = k
2x+3y-z = 1
Give the solution when k=3, describing the relationship of the planes in this instance

i tried to transform the above to reduced row echelon form which gives the solutions
(1 1 3 2; 0 1 -7 -3; 0 0 0 0), this means the system has infinitely many solutions, am i right?
from here, i don't know how to do further, what are the solutions represent? if there are infinitely many solutions, the three planes meet on a line or a plane by the three forms which are 3 coincident planes, intersecting is a plane, 2 coincident planes, intersection is a line, intersection is a line. how can i identify which one is which from the above solutions? thx!

摇得你好滚

how about the second assignment?

摇得你好滚

maths108, assignment 1, No.9 (d)  thank u

没蚊香的黑夜

Hi again...math 108 question 5....my answer is when k=pi/2 or k=pi/4 ,the function is continuous.... is that right? thanks

没蚊香的黑夜

原帖由 303B25 于 2008-3-27 13:06 发表
do the limit for the first one and second one, they must equal to each other,  find the value of k such that as x -> pi/2, first function equal the second function, that will be your solution.

Still not quite clear about this.......

Could you plz break it down? or is there any other good way to understand "continuous"?

Cheers

tokidoki_y

ok.,thanx. ill try to solve it ...

z-score

He wondered if you need to show working and if you need to do it in MATLAB.

没蚊香的黑夜

问一下。。。maths 108的assignment一定要用matlab做吗？ 可以用手写的吗？ 。。。。好像要求过程吧。。。。。

tokidoki_y

um...how about MATHS 108, ASSIGNMENT 1, QUESTION 5., ?

摇得你好滚

ja, thanks a lot