\(4x\left(x-5\right)^2-12\left(4-x\right)^2\)
\(=4\left[x\left(x-5\right)^2-3\left(4-x\right)^2\right]\)
\(=4\left[x\left(x^2-10x+25\right)-3\left(16-8x+x^2\right)\right]\)
\(=4\left(x^3-10x^2+25x-48+24x-3x^2\right)\)
\(=4\left(x^3-13x^2+49x-48\right)\)
#Ayumu