Chúc bạn học tốt !!
a) x(2x²-3)-x²(5x+1)+x²
= 2x³-3x-5x³-x²+x²
= -3x³-3x
b) 3x(x-2)-5x(1-x)-8(x²-3)
=3x²-6x-5x+5x²-8x²+24
= -11x+24
c) $\frac{1}{2}$ x³(6x-3)-x(x²+$\frac{1}{2}$) + $\frac{1}{2}$(x+4)
= $\frac{1}{2}$ . $6x^{4}$ - $\frac{3}{2}$.x² - x³ - $\frac{1}{2}$.x + $\frac{1}{2}$x + 2
= $6x^{4}$ + $\frac{1}{2}$.x³ + 2