10000x = $(9982)^2$ - $(18)^2$

Use the difference of squares identity $a^2 - b^2 = (a - b)(a + b)$. Here $a = 9982$ and $b = 18$, so $(9982 - 18)(9982 + 18) = (9964)(10000)$. Since $10000x = 9964 \times 10000$, $x$ is clearly $9964$.

Many students try to calculate the squares of 9982 and 18 individually, which is time-consuming and prone to arithmetic errors.

This identity is frequently used in 'Simplification' and 'Number Systems' topics to handle large squares that are close to multiples of 100 or 1000.