Question

if a^2-b^2 = 45 and a-b=3, then ab=?

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Answer 1

$a \: - \: b \: = 3$

${(a - b)}^{2} = 9$

${a}^{2} + {b}^{2} - 2ab = 9$

$2ab \: = \: 36$

$ab \: = \: 18$

The question is slightly wrong.

It should be a^2 + b^2 = 45 not what you have written....