a) $\frac{1}{4}\times x(\frac{1}{2}x^{2})\times (-\frac{4}{5}x^{3})=\frac{-1}{10}x^{6}$
b) $0.5x^{m+1}\times 0.8x^{m-1}=0.4x^{2m}$
c) $(x^{2}-3x+\frac{1}{4})(-3x^{3})=-3x^{5}+9x^{4}-\frac{3}{4}x^{3}$;
d) $(x-2)(x^{2}+x-1)-x(x^{2}-1)=-x^{2}-2x+2$
a) $\frac{1}{4}\times x(\frac{1}{2}x^{2})\times (-\frac{4}{5}x^{3})=\frac{-1}{10}x^{6}$
b) $0.5x^{m+1}\times 0.8x^{m-1}=0.4x^{2m}$
c) $(x^{2}-3x+\frac{1}{4})(-3x^{3})=-3x^{5}+9x^{4}-\frac{3}{4}x^{3}$;
d) $(x-2)(x^{2}+x-1)-x(x^{2}-1)=-x^{2}-2x+2$