1. Calculate the value of the expression $a^{2}-c^{2}+b^{2}+2 a b$ if $a=786, b=389$ and $c=175$.
First method:

$a^{2}-c^{2}+b^{2}+2 a b=$

$=a^{2}+2 a b+b^{2}-c^{2}$

$=(a+b)^{2}-c^{2} \quad 2$ POINTS

$=(a+b+c)(a+b-c) \quad 2$ POINTS

By substitution, we get:

$(786+389+175)(786+389-175)=$

$=1350 \cdot 1000$

1 POINT

$=1350000$

1 POINT

.$T O T A L ~ 6$ POINTS

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