1. =2.5xy x x^2y-2/5xy x 5x + 2/5xy x 10y
=2.5x^3y^2-2x^2y+4xy^2
mấy câu khác tương tự=))
1)
a, \(\dfrac{2}{5}xy\left(x^2y-5x+10y\right)\)
\(=\left(\dfrac{2}{5}xy\cdot x^2y\right)-\left(\dfrac{2}{5}xy\cdot5x\right)+\left(\dfrac{2}{5}xy\cdot10y\right)\)
\(=\dfrac{2}{5}x^3y^2-2x^2y+4xy^2\)
b, \(2x\left(x-3\right)+\left(x-2\right)\left(5-2x\right)\)
\(=2x^2-6x+5x-2x^2-10+4x\)
\(=3x-10\)
2)
a, \(3x^2y\left(x^2-3y+2xy^2\right)\)
\(=\left(3x^2y\cdot x^2\right)-\left(3x^2y\cdot3y\right)+\left(3x^2y\cdot2xy^2\right)\)
\(=3x^4y-9x^2y^2+6x^3y^3\)
b, \(\left(x-1\right)\left(x+2020\right)-\left(x+2019\right)\)
\(=x^2+2020x-x-2020-x-2019\)
\(=x^2+2018x-4039\)
3)
a, \(9x^2y\left(xy-2y+7xy^2\right)\)
\(=\left(9x^2y\cdot xy\right)-\left(9x^2y\cdot2y\right)+\left(9x^2y\cdot7xy^2\right)\)
\(=9x^3y^2-18x^2y^2+63x^3y^3\)
b, \(\left(x+1\right)^2+\left(x-1\right)^2-\left(x-1\right)\left(x+1\right)\)
\(=\left(x^2+2x+1\right)+\left(x^2-2x+1\right)-\left(x^2-1\right)\)
\(=x^2+2x+1+x^2-2x+1-x^2+1\)
\(=x^2+3\)
