a) \(\dfrac{1}{2}\)x2 (2x3 - \(\dfrac{2}{5}\) x - 1)
b) (x2 + 2x -3) (-8)
c) -4x5 (x3 - 4x2 + 7x - 3)
d) -5x2 ( 3x2 - 2x3 - x)
e) \(\dfrac{1}{2}\) x3 ( 2x3 - 4x -6)
f) \(\dfrac{3}{5}\) x2 (-\(\dfrac{5}{3}\)x3 - 10x + 5)
g) -\(\dfrac{7}{2}\)x ( \(\dfrac{2}{7}\)x4 + \(\dfrac{3}{14}\)x3 - \(\dfrac{2}{5}\)x2)
Giải gấp giúp mình ạ
\(a.\dfrac{1}{2}x^2\left(2x^3-\dfrac{2}{5}x-1\right)\\ =\dfrac{1}{2}x^2\cdot2x^3-\dfrac{1}{2}x^2\cdot\dfrac{2}{5}x-\dfrac{1}{2}x^2\\ =x^5-\dfrac{1}{5}x^3-\dfrac{1}{2}x^2\\ b.\left(x^2+2x-3\right)\left(-8\right)\\ =\left(-8\right)\cdot x^2+\left(-8\right)\cdot x-3\cdot\left(-8\right)\\ =-8x^2-8x+24\\ c.-4x^5\left(x^3-4x^2+7x-3\right)\\ =-4x^5\cdot x^3-4x^5\cdot\left(-4x^2\right)-4x^5\cdot7x-4x^5\cdot\left(-3\right)\\ =-4x^8+16x^7-28x^6+12x^5\\ d.-5x^2\left(3x^2-2x^3-x\right)\\ =-5x^2\cdot3x^2-5x^2\cdot\left(-2x^3\right)-5x^2\cdot\left(-x\right)\\ =-15x^4+10x^5+5x^3\)
\(e.\dfrac{1}{2}x^3\left(2x^3-4x-6\right)\\ =\dfrac{1}{2}x^3\cdot2x^3-\dfrac{1}{2}x^3\cdot4x-\dfrac{1}{2}x^3\cdot6\\ =x^6-2x^4-3x^3\\ f.\dfrac{3}{5}x^2\left(-\dfrac{5}{3}x^3-10x+5\right)\\ =\dfrac{3}{5}x^3\cdot\left(-\dfrac{5}{3}x^3\right)+\dfrac{3}{5}x^2\cdot\left(-10x\right)+\dfrac{3}{5}x^2\cdot5\\ =-x^6-6x^3+3x^2\\ g.-\dfrac{7}{2}x\left(\dfrac{2}{7}x^4+\dfrac{3}{14}x^3-\dfrac{2}{5}x^2\right)\\ =\dfrac{7}{2}x\cdot\dfrac{2}{7}x^4+\dfrac{7}{2}x\cdot\dfrac{3}{14}x^3-\dfrac{7}{2}x\cdot\dfrac{2}{5}x^2\\ =x^5+\dfrac{3}{4}x^4-\dfrac{7}{5}x^3\)
