Rut gon : A = x|x - 2| / x^2 + 8x - 20 .
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27 tháng 7 2017
\(=\frac{\left(x+1\right)^2}{\left(x-1\right)^2}:\frac{2\left(x+1\right)^2}{4\left(x-1\right)^2}=\frac{\left(x+1\right)^2}{\left(x-1\right)^2}.\frac{4\left(x-1\right)^2}{2\left(x+1\right)^2}=2\)
NH
0
12 tháng 11 2017
Câu a :
\(\dfrac{3x^2-12x+12}{x^4-8x}\)
\(=\dfrac{3\left(x^2-4x+4\right)}{x\left(x^3-8\right)}\)
\(=\dfrac{3\left(x-2\right)^2}{x\left(x-2\right)\left(x^2+2x+4\right)}\)
\(=\dfrac{3\left(x-2\right)}{x\left(x^2+2x+4\right)}\)
Câu b :
\(\dfrac{7x^2+14x+7}{3x^2+3x}\)
\(=\dfrac{7\left(x+1\right)^2}{3x\left(x+1\right)}=\dfrac{7\left(x+1\right)}{3x}\)
29 tháng 6 2019
\(a,\)\(2\left(x-y\right)\left(x+y\right)+\left(x-y\right)^2+\left(x+y\right)^2.\)
\(=\left[\left(x-y\right)+\left(x+y\right)\right]^2=\left(x-y+x+y\right)^2=x^2\)
\(b,\)\(\left(2x-3\right)\left(4x^2+6x+9\right)-\left(54+8x\right)\)
\(=8x^2-27-54-8x=8x^2-8x-81\)
\(c,\)\(\left(3x+y\right)\left(9x^2-3xy+y^2\right)-\left(3x-y\right)\left(9x^2+3xy+y^2\right)\)
\(=27x^3+y^3-\left(27x^3-y^3\right)=2y^3\)
\(d,\)\(\left(a+b+c\right)^2-\left(a-c\right)^2-2ab+2bc\)
\(=a^2+b^2+c^2+2ab+2bc+2ac-a^2+2ac-c^2-2ab+2bc\)
\(=b^2+4bc+4ac\)
J
2
26 tháng 11 2018
1) \(\dfrac{x^2-18x-19}{x^2-1}=\dfrac{x^2-19x+x-19}{\left(x-1\right)\left(x+1\right)}=\dfrac{x\left(x-19\right)+x-19}{\left(x-1\right)\left(x+1\right)}=\dfrac{\left(x-19\right)\left(x+1\right)}{\left(x-1\right)\left(x+1\right)}=\dfrac{x-19}{x-1}\)
2) \(\dfrac{x\left(4x^2-8x+4\right)}{2x^3-2x^2}=\dfrac{4x\left(x^2-2x+1\right)}{2x^2\left(x-1\right)}=\dfrac{4x\left(x-1\right)^2}{2x^2\left(x-1\right)}=\dfrac{2\left(x-1\right)}{x}\)
17 tháng 9 2020
Bài 1
( x - y )2 - 4
= ( x - y )2 - 22
= ( x - y - 2 )( x - y + 2 )
x2 - 16( x + y )2
= x2 - 42( x + y )2
= x2 - ( 4x + 4y )2
= ( x2 - 4x - 4y )( x2 - 4x + 4y )
8x3 + 36x2y + 54xy2 + 27y3
= ( 2x )3 + 3.( 2x )2.3y + 3.2x.( 3y )2 + ( 3y )3
= ( 2x + 3y )3
Bài 2.
a) ( x2 + 4 )( x2 - 4 ) - ( x2 + 1 )( x2 - 1 )
= [ ( x2 )2 - 42 ] - [ ( x2 )2 - 12 ]
= x4 - 16 - x4 + 1
= -15
b) ( y - 3 )( y + 3 )( y2 + 9 )( y2 + 2 )( y2 - 2 )
= [ ( y - 3 )( y + 3 )( y2 + 9 ) ][ ( y2 + 2 )( y2 - 2 ) ]
= { [ ( y - 3 )( y + 3 ) ]( y2 + 9 ) }[ ( y2 )2 - 22 ]
= [ ( y2 - 9 )( y2 + 9 ) ]( y4 - 4 )
= ( y4 - 81 )( y4 - 4 )
= y4( y4 - 4 ) - 81( y4 - 4 )
= y8 - 4y4 - 81y4 + 324
= y8 - 85y4 + 324
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