Tính:
a) 3x(5x^2 – 3x – 1)
b) (x^2 + 2xy – 3)
c) 1/2x^2y(2x^3 – 2/5xy^2 – 1)
d) 2x(x – 5) – x(3 + 2x)
HELP…..
Tính:
a) 3x(5x^2 – 3x – 1)
b) (x^2 + 2xy – 3)
c) 1/2x^2y(2x^3 – 2/5xy^2 – 1)
d) 2x(x – 5) – x(3 + 2x)
HELP…..
a) 3x(5$x^{2}$-3x-1)
=3×5$x^{2}$-3x3x-3x
=15$x^{3}$-9$x^{2}$-3x
b) ($x^{2}$+2xy-3)(-xy)
=-xy$x^{2}$-xy2xy+3xy
=-$x^{3}$y-2$x^{2}$$y^{2}$+3xy
c) $\frac{1}{2}$$x^{2}$y(2$x^{3}$-$\frac{2}{5}$x$y^{2}$-1)
=$\frac{1}{2}$$x^{2}$y2$x^{3}$-$\frac{1}{2}$$x^{2}$y.$\frac{2}{5}$x$y^{2}$-$\frac{1}{2}$$x^{2}$y
=$x^{5}$y-$\frac{1}{5}$$x^{3}$$y^{3}$-$\frac{1}{2}$$x^{2}$y
d) 2x(x-5)-x(3+2x)
=2xx-2×5-3x-2xx
=2$x^{2}$-10x-3x-2$x^{2}$
=2$x^{2}$-2$x^{2}$-10x-3x
=(2$x^{2}$-2$x^{2}$)-(10x+3x)
=-13x
Đáp án:
\(a,\ 3x(5x^2-3x-1)=15x^3-9x^2-3x\\ b,\ (x^2+2xy-3)(-xy)=-x^3y-2x^2y^2+3xy\\ c,\ \dfrac{1}{2}x^2y\bigg(2x^3-\dfrac{2}{5}xy^2-1\bigg)=x^5y-\dfrac{1}{5}x^3y^3-\dfrac{1}{2}x^2y\\ d,\ 2x(x-5)-x(3+2x)=-13x\)
Giải thích các bước giải:
\(a,\ 3x(5x^2-3x-1)=15x^3-9x^2-3x\\ b,\ (x^2+2xy-3)(-xy)=-x^3y-2x^2y^2+3xy\\ c,\ \dfrac{1}{2}x^2y\bigg(2x^3-\dfrac{2}{5}xy^2-1\bigg)=x^5y-\dfrac{1}{5}x^3y^3-\dfrac{1}{2}x^2y\\ d,\ 2x(x-5)-x(3+2x)\\ =2x^2-10x-3x-2x^2\\ =(2x^2-2x^2)+(-10x-3x)\\ =-13x\)
chúc bạn học tốt!