Question

$9a^2-\frac{12}{5}a+\frac{4}{25}$ can be expressed as ____.

• A. ${(a-\frac{2}{5})}^2$
• B. ${(3a-\frac{2}{5})}^2$
• C. ${(2a-\frac{2}{5})}^2$
• D. ${(a-\frac{5}{2})}^2$

Answer 1

The correct option is B ${(3a-\frac{2}{5})}^2$

$9a^2-\frac{12}{5}a+\frac{4}{25}=(3a{)}^2-2\times 3a\times \frac{2}{5}+{\left(\frac{2}{5}\right)}^2$
$\text{[Using identity:}(a-b{)}^2=a^2-2ab+b^2]$
$={(3a-\frac{2}{5})}^2$