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I am reading the book "Several Real Variables" by Shmuel Kantorovitz ... ...
I am currently focused on Chapter 2: Derivation ... ...
I need help with another element of the proof of Kantorovitz's Proposition on pages 61-62 ...
Kantorovitz's Proposition on pages 61-62 reads as follows:
In the above proof we read the following:
" ... ... Formula 2.4 is trivially true in case ##h_j = 0##, and by (2.2) - (2.4)
##f(x + h) - f(x) = \sum_{ j = 1}^k [ F_j ( h_j ) - F_j (0) ]##
##= \sum_j h_j \frac{ \partial f }{ \partial x_j } ( x + h^{ j - 1 } + \theta_j h_j e^j )## ... ... ... ... ... "I have tried to derive ##f(x + h) - f(x) = \sum_{ j = 1}^k [ F_j ( h_j ) - F_j (0) ]## but did not succeed ...
... can someone please show how ##f(x + h) - f(x)## equals ##\sum_{ j = 1}^k [ F_j ( h_j ) - F_j (0) ]## ...Also can someone show how the above equals ##\sum_j h_j \frac{ \partial f }{ \partial x_j } ( x + h^{ j - 1 } + \theta_j h_j e^j )## ... ...
Help will be much appreciated ... ...
Peter
I am currently focused on Chapter 2: Derivation ... ...
I need help with another element of the proof of Kantorovitz's Proposition on pages 61-62 ...
Kantorovitz's Proposition on pages 61-62 reads as follows:
In the above proof we read the following:
" ... ... Formula 2.4 is trivially true in case ##h_j = 0##, and by (2.2) - (2.4)
##f(x + h) - f(x) = \sum_{ j = 1}^k [ F_j ( h_j ) - F_j (0) ]##
##= \sum_j h_j \frac{ \partial f }{ \partial x_j } ( x + h^{ j - 1 } + \theta_j h_j e^j )## ... ... ... ... ... "I have tried to derive ##f(x + h) - f(x) = \sum_{ j = 1}^k [ F_j ( h_j ) - F_j (0) ]## but did not succeed ...
... can someone please show how ##f(x + h) - f(x)## equals ##\sum_{ j = 1}^k [ F_j ( h_j ) - F_j (0) ]## ...Also can someone show how the above equals ##\sum_j h_j \frac{ \partial f }{ \partial x_j } ( x + h^{ j - 1 } + \theta_j h_j e^j )## ... ...
Help will be much appreciated ... ...
Peter