Evaluate Using Identity

\[ (399)^2 \]

Solution:

Using identity:

\[ (a-b)^2 = a^2 – 2ab + b^2 \]

\[ 399^2 = (400-1)^2 \]

\[ = (400)^2 – 2(400)(1) + (1)^2 \]

\[ = 160000 – 800 + 1 \]

\[ = 159201 \]

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