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Question-72671




Question Number 72671 by aliesam last updated on 31/Oct/19
Commented by kaivan.ahmadi last updated on 31/Oct/19
a)  ∣x_(n+1) −x_n ∣≤c∣x_n −x_(n−1) ∣≤c^2 ∣x_(n−1) −x_(n−2) ∣≤...≤c^n ∣x_1 −x_0 ∣  b)  ∣x_(n+1) −x_0 ∣=∣(x_(n+1) −x_n )+(x_n −x_(n−1) )+...+(x_1 −x_0 )∣≤  ∣x_(n+1) −x_n ∣+∣x_n −x_(n−1) ∣+...+∣x_1 −x_0 ∣≤  c^n ∣x_1 −x_0 ∣+c^(n−1) ∣x_1 −x_0 ∣+...+∣x_1 −x_0 ∣=  (c^n +c^(n−1) +...+1)∣x_1 −x_0 ∣  c)  x_(n+1) −x_k =(x_(n+1) −x_n )+(x_n −x_(n−1) )+...+(x_(k+1) −x_k )⇒  c  is clear.
a)xn+1xn∣⩽cxnxn1∣⩽c2xn1xn2∣⩽cnx1x0b)xn+1x0∣=∣(xn+1xn)+(xnxn1)++(x1x0)∣⩽xn+1xn+xnxn1++x1x0∣⩽cnx1x0+cn1x1x0++x1x0∣=(cn+cn1++1)x1x0c)xn+1xk=(xn+1xn)+(xnxn1)++(xk+1xk)cisclear.

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