Question

evaluate using identities .
(0.98)²
991*1009

Answer 1

${0.98}^{2} = {(1 -0.02)}^{2} \\ {1}^{2} - 2 \times 1 \times 0.02 + {0.02}^{2} \\ = 1 + 0.0004 - 0.04$
$991 \times 1009 = (1000 - 9)(1000 + 9) \\ {1000}^{2} - {9}^{2}$
Hope this helps.