Evaluate Using Identity

\[ 991 \times 1009 \]

Solution:

Using identity:

\[ (a-b)(a+b)=a^2-b^2 \]

\[ 991 \times 1009 = (1000-9)(1000+9) \]

\[ = (1000)^2 – (9)^2 \]

\[ = 1000000 – 81 \]

\[ = 999919 \]

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