1. Calculate: $12345^{2}+12353^{2}-2 \cdot 12349^{2}$.
First method:

$12345^{2}+12353^{2}-2 \cdot 12349^{2}=$

$=12345^{2}-12349^{2}+12353^{2}-12349^{2}=\quad 1$ POINT

$=(12345-12349) \cdot(12345+12349)+(12353-12349) \cdot(12353+12349)=\quad 2$ POINTS

$\begin{array}{ll}=-4 \cdot 24694+4 \cdot 24702= & 1 \text{POINT}\end{array}$

$=4 \cdot(24702-24694)=\quad 1$ POINT

$\begin{array}{ll}= & =32 \\ 1 \text{POINT}\end{array}$

TOTAL 6 POINTS

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