Step-by-step explanation:
[tex] {(3a - \frac{1}{6} b)}^{2} = 9 {a}^{2} - \frac{1}{2} ab - \frac{1}{2} ab + \frac{1}{36} {b}^{2} [/tex]
[tex]= 9 {a}^{2} - ab + \frac{1}{36} {b}^{2} [/tex]
