Mới thi sáng nay.
Đề thi: ktgk_k51-a3_gt5_2.pdf
Đáp án:
Có hai kết quả sau khá hay và đẹp (với sự giúp đỡ của TS. Đ.A. Tuấn)
Trong trường hợp 2 chiều
.
còn trong 3 chiều thì
.
Dự đoán trong trường hợp n chiều thì kết quả sẽ là
.
Có 2 công thức sau đây mà chúng ta nên biết.
Chứng minh. By definition, . Now let , and let’s solve the equation for x:
and now solving for e^x we get
(we take the + sign because the exponential is always positive). Therefore we may conclude).
Since
then
Thus
Let , then for all ,
If , then
Proof. We consider two cases separately.
Case . The strict convexity of implies that for any
Writing instead of we obtain
or
Using Clarkson inequality
we arrive at
or
Repeating this procedure we ca replace the constant
by
By iteration one obtains the constant
Case . Fix and expand the real function
Using Taylor formula
Then, provided for all ,
At the same time
Schwartz inequality yields
Now,
Lastly
For students sitting for the examination session in January 2008:
Algebra | Linear Algebra | Mathematical Programming
Analysis | Complex Analysis | Numerical Analysis | Real Analysis
For students sitting for the examination session in August 2008 or later:
Algebra | Analysis 1 | Analysis 2 | Computational Mathematics
Let be a Banach space with closed in and . For define
.
Let be such that
.
If satisfies condition with
where
then is a critical point of .