Question

Question 6(vii)
Using identities, evaluate:
$78\times 82$

Answer 1

$78\times 82=(80-2)\times (80+2)=(80{)}^2-(2{)}^2$
$\left[Usingidentity\right(a-b\left)\right(a+b)=a^2-b^2]$
$=6400-4=6396$