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\(A=\frac{2x-y}{3x-y}+\frac{5y-x}{3x+y}\)
\(=\frac{\left(2x-y\right)\left(3x+y\right)+\left(5y-x\right)\left(3x-y\right)}{\left(3x-y\right)\left(3x+y\right)}\)
\(=\frac{3x^2+15xy-6y^2}{9x^2-y^2}\)
\(=\frac{3\left(x^2+5xy-2y^2\right)}{9x^2-y^2}\)
\(=\frac{3\left(10x^2+5xy-3y^2-9x^2+y^2\right)}{9x^2-y^2}\)
\(=-\frac{3\left(9x^2-y^2\right)}{9x^2-y^2}\)
= - 3 (đpcm)
~~~
\(A=\frac{1}{x}+\frac{1}{x+2}+\frac{x-2}{x^2+2x}\)
\(=\frac{x+2+x+x-2}{x^2+2x}\)
\(=\frac{3x}{x\left(x+2\right)}\)
\(=\frac{3}{x+2}\)
\(A\in Z\)
\(\Leftrightarrow3⋮x+2\)
\(\Leftrightarrow x+2\in\text{Ư}\left(3\right)=\left\{-3:-1;1;3\right\}\)
\(\Leftrightarrow x\in\left\{-5;-3;-1;1\right\}\)
Bài 2:
\(\dfrac{1}{x}+\dfrac{1}{x+2}+\dfrac{x-2}{x\left(x+2\right)}\)
\(=\dfrac{x+x+2+x-2}{x\left(x+2\right)}=\dfrac{3x}{x\left(x+2\right)}=\dfrac{3}{x+2}\)
Để 3/x+2 là số nguyên thì \(x+2\in\left\{1;-1;3;-3\right\}\)
hay \(x\in\left\{-1;-3;1;-5\right\}\)
1) 2x + 2y - x(x+y)
= 2(x + y) - x(x + y)
= (2 - x)(x + y)
2/ 5x2 - 5xy -10x + 10y
= 5x(x - y) - 10(x - y)
= (5x - 10(x - y)
3/ 4x2 + 8xy - 3x - 6y
= 4x(x + 2y) - 3(x + 2y)
= (4x - 3)(x + 2y)
1) 2x + 2y - x(x + y)
= 2(x + y) - x(x + y)
= (2 - x)(x + y)
2) 5x2 - 5xy - 10x + 10y
= 5x(x - y) - 10(x - y)
= (5x - 10)(x - y)
= 5(x - 2)(x - y)
3) 4x2 + 8xy - 3x - 6y
= 4x(x + 2y) - 3(x + 2y)
= (4x - 3)(x + 2y)
4) 2x2 + 2y2 - x2z + z - y2z - 2
= 2(x2 + y2 - z(x2 + y2) - (2 - z)
= (2 - z)(x2 + y2) - (2 - z)
= (2 - z)(x2 + y2)
5) x2 + xy - 5x - 5y
= x(x + y) - 5(x + y)
= (x - 5)(x + y)
6) x(2x - 7) - 4x + 14
= x(2x - 7) - 2(2x - 7)
= (x - 2)(2x - 7)
7)x2 - 3x + xy - 3y
= x(x + y) - 3(x + y)
= (x - 3)(x + y)
tìm x,biết:
a)x^3-6x^2+12x-9=0
b)8x^3+12x^3+6x-26=0
~ giúp mk nha,cảm ơn nhiều ~
\(a,-2xy^2\left(x^3y-2x^2y^2+5xy^3\right)\\ =-2x^4y^3+4x^3y^4-10x^2y^5\\ b,\left(-2x\right)\left(x^3-3x^2-x+1\right)\\ =-2x^4+6x^3+2x^2-2x\\ c,\left(-10x^3+\dfrac{2}{5}y-\dfrac{1}{3}z\right)\left(-\dfrac{1}{2}zy\right)\\ =5x^3yz-\dfrac{1}{5}y^2z+\dfrac{1}{6}yz^2\\ d,3x^2\left(2x^3-x+5\right)=6x^5-3x^3+15x^2\\ e,\left(4xy+3y-5x\right)x^2y=4x^3y^2+3x^2y^2-5x^3y\\ f,\left(3x^2y-6xy+9x\right)\left(-\dfrac{4}{3}xy\right)\\ =-4x^3y^2+8x^2y^2-12x^2y\)
