Bài 1: Làm tính nhân:
a) 3x(5x2 - 2x - 1) ;
b) (x2 + 2xy - 3)(-xy) ;
c) \(\dfrac{1}{2}\)x2y(2x3 - \(\dfrac{2}{5}\)xy2 - 1).
Bài 2: Rút gọn các biểu thức sau:
a) x(2x2 - 3) - x2(5x + 1) + x2 ;
b) 3x(x - 2) - 5x(1 - x) - 8(x2 - 3) ;
c) \(\dfrac{1}{2}\)x2(6x - 3) - x (x2 + \(\dfrac{1}{2}\)) + \(\dfrac{1}{2}\)(x + 4).
Bài 1:
a,\(3x\left(5x^2-2x-1\right)\)
\(=3x.5x^2-3x.2x-3x=15x^3-6x^2-3x\)
b,\(\left(x^2+2xy-3\right)\left(-xy\right)\)
\(=x^2.\left(-xy\right)+2xy.\left(-xy\right)-3.\left(-xy\right)\)
\(=-x^3y-2x^2y^2+3xy\)
c,\(\dfrac{1}{2}x^2y\left(2x^3-\dfrac{2}{5}xy^2-1\right)\)
\(=\dfrac{1}{2}x^2y.\left(2x^3\right)-\dfrac{1}{2}x^2y.\dfrac{2}{5}xy^2-\dfrac{1}{2}x^2y\)
\(=x^5y-\dfrac{1}{5}x^3y^3-\dfrac{1}{2}x^2y\)
Chúc bạn học tốt!!!
Bài 1:
a) \(3x\left(5x^2-2x-1\right)\\ =15x^3-6x^2-3x\)
b) \(\left(x^2+2xy-3\right)\left(-xy\right)\\ =-x^3y-2x^2y+3xy\)
c) \(\dfrac{1}{2}x^2y\left(2x^3-\dfrac{2}{5}xy^2-1\right)\\ =x^5y-\dfrac{1}{5}x^3y^3-\dfrac{1}{2}x^2y\)
Bài 2:
a) \(x\left(2x^2-3\right)-x^2\left(5x+1\right)+x^2\\ =2x^3-3x-5x^3-x^2+x^2\\ =-3x^3-3x\)
b) \(3x\left(x-2\right)-5x\left(1-x\right)-8\left(x^2-3\right)\\ =3x^2-6x-5x+5x^2-8x^2+24\\ =x+24\)
c) \(\dfrac{1}{2}x^2\left(6x-3\right)-x\left(x^2+\dfrac{1}{2}\right)+\dfrac{1}{2}\left(x+4\right)\\ =3x^3-\dfrac{3}{2}x^2-x^3-\dfrac{1}{2}x+\dfrac{1}{2}x+2\\ =2x^3-\dfrac{3}{2}x^2+2\)
Bài 2:
a,\(x.\left(2x^2-3\right)-x^2\left(5x+1\right)+x^2\)
\(=2x^3-3x-5x^3+x^2+x^2\)
\(=\left(2x^3-5x^3\right)+\left(x^2+x^2\right)-3x\)
\(=-3x^3+2x^2-3x\)
b,\(3x\left(x-2\right)-5x\left(1-x\right)-8\left(x^2-3\right)\)
\(=3x^2-6x-5x+5x^2-8x^2+24\)
\(=\left(3x^2+5x^2-8x^2\right)+\left(-6x-5x\right)+24\)
\(=-11x+24\)
c,\(\dfrac{1}{2}x^2\left(6x-3\right)-x\left(x^2+\dfrac{1}{2}\right)+\dfrac{1}{2}\left(x+4\right)\)
\(=\dfrac{1}{2}x^2.6x-\dfrac{1}{2}x^2.3-x^3+\dfrac{1}{2}x+\dfrac{1}{2}x+2\)
\(=3x^3-\dfrac{3}{2}x^2-x^3+\dfrac{1}{2}x+\dfrac{1}{2}x+2\)
\(=\left(3x^3-x^3\right)-\dfrac{3}{2}x^2+\left(\dfrac{1}{2}x+\dfrac{1}{2}x\right)+2\)
\(=2x^3-\dfrac{3}{2}x^2+x+2\)
Chúc bạn học tốt!!!
bài 1:
a) 3x(5x2 - 2x -1)
<=> 15x3- 6x2- 3x
b) (x2+2xy-3)(-xy)
<=> -x3y-2x2y2+3xy
c) 1/2x2y(2x3-2/5xy2-1)
<=> x5y-1/5x3y3-1/2x2y
bài 2:
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) 1/2x2(6x-3)-x(x2+1/2)+1/2(x+4)
<=> 3x3-3/2x2-x3-1/2x+1/2x+2
<=> 2x3-3/2x2+2
:))))))))
