Question

Factorise $98(a+b{)}^2-2$

• A. $2[7a+7b+1][7a+b-1]$
• B. $2[7a-7b+1][7a+b-1]$
• C. $2[7a+7b-1][7a+b-1]$
• D. $2[7a+7b+1][7a+b+1]$

Answer 1

The correct option is A $2[7a+7b+1][7a+b-1]$

$98(a+b{)}^2-2$
$=2\left[49\right(a+b{)}^2-1^2]$
$=2\left[\right(7(a+b){)}^2-1^2]$
We know that,
{ $a^2-b^2=(a+b)(a-b)$}
$=2[7a+7b+1][7a+7b-1]$