a) $x^{2}$ . ( $5x^{3}$ – x – $\frac{1}{2}$ ) = $5x^{5}$ – $x^{3}$ – $\frac{1}{2}$ $x^{2}$
b) ( 3xy – $x^{2}$ y) . $\frac{2}{3}$ $x^{3}$ $y^{2}$ – $\frac{2}{3}$ $x^{4}$ $y^{2}$
c) ( $4x^{3}$ – 5xy + 2x ) . ( -$\frac{1}{2}$xy ) = -$2x^{4}$y + $\frac{5}{2}$ $x^{2}$ $y^{2}$ – 1$x^{2}$ y
a) $x^{2}$ . ( $5x^{3}$ – x – $\frac{1}{2}$ ) = $5x^{5}$ – $x^{3}$ – $\frac{1}{2}$ $x^{2}$ b) ( 3xy – $x^{2}$ y) . $\frac{2}{3}$ $x^{3}$ $y^{2}
By Ruby
a) $x^2.(5x^3-x-\dfrac{1}{2})$
$=(x^2.5x^3)-(x^2.x)-(x^2.\dfrac{1}{2})$
$=5x^5-x^3-\dfrac{1}{2}x^2$
b) $(3xy-x^2y).\dfrac{2}{3}x^3y^2-\dfrac{2}{3}x^4y^2$
$=(\dfrac{2}{3}x^2y^2.3xy)-(\dfrac{2}{3}x^3y^2.x^2y)-\dfrac{2}{3}x^4y^2$
$=2x^4y^3-\dfrac{2}{3}x^5y^3-\dfrac{2}{3}x^4y^2$
c) $(4x^3-5xy+2x).(-\dfrac{1}{2}xy)$
$=(-\dfrac{1}{2}xy.4x^3)-(-\dfrac{1}{2}xy.5xy)+(-\dfrac{1}{2}xy.2x)$
$=-2x^4y+\dfrac{5}{2}x^2y^2-1x^2y$
$=-2x^4y+\dfrac{5}{2}x^2y^2-x^2y$
Đáp án:
Giải thích các bước giải:
$a,x^2.\left (5x^3-x-\dfrac{1}{2} \right )$
$=5x^5-x^3-\dfrac{1}{2}x^2$
$b,(3xy-x^2y).\dfrac{2}{3}x^3y^2-\dfrac{2}{3}x^4y^2$
$=2x^4y^3-\dfrac{2}{3}x^5y^3-\dfrac{2}{3}x^4y^2$
$c,(4x^3-5xy+2x).\left (-\dfrac{1}{2}xy \right )$
$=-2x^4y+\dfrac{5}{2}x^2y^2-x^2y$