Question
Expand the following, using suitable identities.$\Big(\frac{2\text{a}}{3}+\frac{\text{b}}{3}\Big)\Big(\frac{2\text{a}}{3}-\frac{\text{b}}{3}\Big)$
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Answer
$\Big(\frac{2\text{a}}{3}+\frac{\text{b}}{3}\Big)\Big(\frac{2\text{a}}{3}-\frac{\text{b}}{3}\Big)$$=\Big(\frac{2\text{a}}{3}\Big)^2-\Big(\frac{\text{b}}{3}\Big)^2$
$=\frac{4}{9}\text{a}^2-\frac{1}{9}\text{b}^2$
$=\frac{4}{9}\text{a}^2-\frac{1}{9}\text{b}^2$
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