Bài 6:
`a)(10x^2-5x):(-5x)-(x-3)=7(x\ne0)`
`10x^2:(-5x)+(-5x):(-5x)-x+3=7`
`-2x+1-x+3=7`
`-3x+4=7`
`-3x=3`
`x=3/(-3)=-1(tm)`
Vậy: `x=-1`
`b)(2x^4-5x^3+x^2):(-1/2x^2)+4(x+2)(x-2)=10(x\ne0)`
`2x^4:(-1/2x^2)-5x^3:(-1/2x^2)+x^2:(-1/2x^2)+4(x^2-2^2)=10`
`-4x^2+10x-2+4(x^2-4)=10`
`-4x^2+10x-2+4x^2-16=10`
`10x-18=10`
`10x=28`
`x=28/10=14/5(tm)`
Vậy: `...`
Bài 6:
a: ĐKXĐ: x<>0
\(\left(10x^2-5x\right):\left(-5x\right)-\left(x-3\right)=7\)
=>\(-\frac{10x^2}{5x}+\frac{5x}{5x}-x+3=7\)
=>-2x+1-x+3=7
=>-3x+4=7
=>-3x=3
=>x=-1(nhận)
b: ĐKXĐ: x<>0
\(\left(2x^4-5x^3+x^2\right):\left(-\frac12x^2\right)+4\left(x-2\right)\left(x+2\right)=10\)
=>\(-2x^4:\frac12x^2+5x^3:\frac12x^2-x^2:\frac12x^2+4\left(x^2-4\right)=10\)
=>\(-4x^2+10x-2+4x^2-16=10\)
=>10x-18=10
=>10x=28
=>\(x=\frac{28}{10}=\frac{14}{5}\left(nhận\right)\)
Bài 5:
\(P=5\left(\frac{2x}{5}-1\right)+\left(18x^2-12x\right):\left(-6x\right)-\left(3x-1\right)\)
\(=2x-5-\frac{18x^2}{6x}+\frac{12x}{6x}-3x+1\)
=2x-5-3x+2-3x+1
=-4x-2
Khi x=-15/4 thì \(P=-4\cdot\frac{-15}{4}-2=15-2=13\)
Bài 4:
a: \(\left(-4x^4y+3x^2y^2-8x^3y^4\right):\left(2x^2y\right)\)
\(=-\frac{4x^4y}{2x^2y}+\frac{3x^2y^2}{2x^2y}-\frac{8x^3y^4}{2x^2y}=-2x^2+\frac32y-4xy^2\)
b: \(\left(x^5-4x^2y+3xy^2\right):\left(-\frac12x\right)\)
\(=-x^5:\frac12x+4x^2y:\frac12x-3xy^2:\frac12x\)
\(=-2x^4+8xy-6y^2\)
c: \(\left(6x^2y^2+3x^2y^3-15xy\right):\left(3xy\right)\)
\(=\frac{6x^2y^2}{3xy}+\frac{3x^2y^3}{3xy}-\frac{15xy}{3xy}=2xy+xy^2-5\)
d: \(8x^2y^2+2x^4y^3:\left(-2x^2y\right)=8x^2y^2-x^2y^2=7x^2y^2\)
e: \(7xy^2+15x^3y^4:\left(-12x^2y^2\right)=7xy^2-\frac54xy^2=\frac{23}{4}xy^2\)
