Expand and simplify \( (7 a-3)^{2} \)

To expand and simplify \( (7a - 3)^2 \), we can use the formula \( (x - y)^2 = x^2 - 2xy + y^2 \). Here, \( x = 7a \) and \( y = 3 \). First, calculate \( (7a)^2 = 49a^2 \). Next, calculate \( 2(7a)(3) = 42a \). Finally, calculate \( 3^2 = 9 \). Now combine these results: \[ (7a - 3)^2 = 49a^2 - 42a + 9 \] So, the expanded and simplified form is \( 49a^2 - 42a + 9 \).