(9а + 3)²

To expand the expression \((9a + 3)^2\), you can use the formula for the square of a binomial, which is given by:

\[ (x + y)^2 = x^2 + 2xy + y^2 \]

In this case, let \(x = 9a\) and \(y = 3\).

Now, applying the formula:

1. \(x^2 = (9a)^2 = 81a^2\)
2. \(y^2 = 3^2 = 9\)
3. \(2xy = 2 \cdot (9a) \cdot 3 = 54a\)

Now, putting it all together:

\[ (9a + 3)^2 = 81a^2 + 54a + 9 \]

So, the expanded form of \((9a + 3)^2\) is:

\[ 81a^2 + 54a + 9 \]