(a+7)²=

To expand the expression \((a + 7)^2\), you use the formula for the square of a binomial: \[ (a + b)^2 = a^2 + 2ab + b^2 \] In this case, \(a\) is \(a\) and \(b\) is \(7\). Applying the formula, we get: \[ (a + 7)^2 = a^2 + 2 \cdot a \cdot 7 + 7^2 \] \[ = a^2 + 14a + 49 \] So, \((a + 7)^2 = a^2 + 14a + 49\).