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Moscow Mathematical Olympiad
1952 Moscow Mathematical Olympiad
214
MMO 214 Moscow MO 1952 |x| < 1, |y| < 1 => |(x - y/(1-xy)| <1
MMO 214 Moscow MO 1952 |x| < 1, |y| < 1 => |(x - y/(1-xy)| <1
Source:
August 8, 2019
inequalities
algebra
absolute value
Moscow
Problem Statement
Prove that if
∣
x
∣
<
1
|x| < 1
∣
x
∣
<
1
and
∣
y
∣
<
1
|y| < 1
∣
y
∣
<
1
, then
∣
x
−
y
1
−
x
y
∣
<
1
\left|\frac{x - y}{1 -xy}\right|< 1
1
−
x
y
x
−
y
<
1
.
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