Solve \( (r-3)^{2} \)

To expand \( (r-3)^{2} \), you'll use the formula for the square of a binomial, which is \( (a-b)^{2} = a^{2} - 2ab + b^{2} \). Here, \( a = r \) and \( b = 3 \). Squaring \( r \) gives \( r^2 \), squaring \( 3 \) gives \( 9 \), and multiplying \( 2 \times r \times 3 \) gives \( 6r \). So, the expansion is: \[ (r-3)^{2} = r^{2} - 6r + 9. \] Now you've got a lovely quadratic expression!