a: Ta có: \(\left(4x-6\right)^2-16\left(x-3\right)^2\)
\(=16x^2-48x+36-16x^2+96x-144\)
\(=48x-108\)
\(=48\cdot\left(-7\right)-108\)
\(=-444\)
b: Ta có: \(\left(x-1\right)\left(x^2+x+1\right)+\left(x+3\right)\left(x^2-3x+9\right)\)
\(=x^3-1+x^3+27\)
\(=2x^3+26\)
\(=-2+26=24\)