Tính giá trị của các biểu thức sau

a) $\frac{3^{12}+3^{15}}{1+3^3}$

$=\frac{3^{12}+3^{12+3}}{1+3^3}$

$=\frac{3^{12}+3^{12}{.3}^3}{1+3^3}$

$=\frac{3^{12}.\left(1+3^3\right)}{1+3^3}$

$=3^{12}$

b) $2:{\left(\frac{1}{2}-\frac{2}{3}\right)}^2+{\mathrm{0,125}}^3{.8}^3-{\left(-12\right)}^4:6^4$

$=2:{\left(\frac{3}{6}-\frac{4}{6}\right)}^2+{\left(\mathrm{0,125.8}\right)}^3-\frac{{\left(-12\right)}^4}{6^4}$

$=2:{\left(\frac{-1}{6}\right)}^2+{\left(1\right)}^3-\frac{{12}^4}{6^4}$

$=2:\frac{{\left(-1\right)}^2}{6^2}+1-{\left(\frac{12}{6}\right)}^4$

$=2:\frac{1}{6^2}+1-2^4$

= 2.6² + 1 – 2⁴

= 2.36 + 1 – 16

= 72 + 1 – 16

= 57