a)
[tex]9(3 {a}^{2} + 5a) - 15a(3 - 6a) = 27 {a}^{2} + 45a - 45a + 90 {a}^{2} = 117 {a}^{2} = 117 \times {( - \frac{1}{3}) }^{2} = 117 \times \frac{1}{9} = 13 [/tex]
b)
[tex]4a(3b - 6) - 2b(6a + 1) = 12ab - 24a - 12ab - 2b = - 24a - 2b = - 24 \times ( - \frac{1}{4} ) - 2 \times \frac{1}{2} = 6 - 1 = 5[/tex]
