Tính ​\(x(1-3 x)(4-3 x)-(x-4)(3 x+5)\)

* Hướng dẫn giải

 \(\begin{aligned} &\text { } x(1-3 x)(4-3 x)-(x-4)(3 x+5) \\ &=\left(x-3 x^{2}\right)(4-3 x)-(x-4)(3 x+5) \\ &=\left(4 x-3 x^{2}-12 x^{2}+9 x^{3}\right)-\left(3 x^{2}+5 x-12 x-20\right) \\ &=\left(9 x^{3}-15 x^{2}+4 x\right)-\left(3 x^{2}-7 x-20\right) \\ &=9 x^{3}-15 x^{2}+4 x-3 x^{2}+7 x+20 \\ &=9 x^{3}-18 x^{2}+11 x+20 \end{aligned}\)