Compute $69 \times 71$ using identities.

Compute $69 \times 71$ using identities.
  1. $4899$
  2. $4900$
  3. $4901$
  4. $4889$

Solution

$(70-1)(70+1) = 70^{2} - 1 = 4900 - 1 = 4899$.

Asked in: IMO

Practice more ALGEBRAIC EXPRESSIONS AND IDENTITIES questions on Aicharya