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\(\dfrac{x^3+8}{x^2+2x+1}.\dfrac{x^2+3x+2}{1-x^2}\left(x\ne\pm1\right)\\ =\dfrac{x^3+2^3}{\left(x+1\right)^2}.\dfrac{\left(x^2+x\right)+\left(2x+2\right)}{1^2-x^2}\\ =\dfrac{\left(x+2\right)\left(x^2-2x+4\right)}{\left(x+1\right)^2}.\dfrac{x\left(x+1\right)+2\left(x+1\right)}{\left(1-x\right)\left(1+x\right)}\\ =\dfrac{\left(x+2\right)\left(x^2-2x+4\right)}{\left(x+1\right)^2}.\dfrac{\left(x+2\right)\left(x+1\right)}{\left(1-x\right)\left(x+1\right)}\\ =\dfrac{\left(x+2\right)^2\left(x^2-2x+4\right)}{\left(1-x\right)\left(x+1\right)^2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Lời giải:
$\frac{x^3+8}{x^2-2x+1}.\frac{x^2+3x+2}{1-x^2}=\frac{(x^3+8)(x^2+3x+2)}{(x^2-2x+1)(1-x^2)}$
$=\frac{(x+2)(x^2-2x+4)(x+1)(x+2)}{(x-1)^2(1-x)(x+1)}$
$=\frac{(x+2)^2(x^2-2x+4)}{-(x-1)^3}$
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{x^2+3x-4}{x-1}=\dfrac{x^2+4x-x-4}{\left(x-1\right)}=\dfrac{\left(x+4\right)\left(x-1\right)}{x-1}=x+4\)
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\(\left(-x^2y^5\right)^2:\left(-x^2y^5\right)=-x^2y^5=-\left(\dfrac{1}{2}\right)^2.\left(-1\right)^5=-\dfrac{1}{4}.\left(-1\right)=\dfrac{1}{4}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
4) (3x-2)(x-3)= 3x(x-3)-2(x-3)
=3x.x+3x.(-3)-2.x-2.(-3)
=\(3x^2\)-9x-4x+6
=\(3x^2\)+(-9x-4x)+6
=\(3x^2\)-13x+6
5) (2x+1)(x+3)=2x(x+3)+1(x+3)
=2x.x+2x.3+1.x+1.3
=\(2x^2\)+6x+1x+3
=\(2x^2\)+(6x+1x)+3
=\(2x^2\)+7x+3
6) (x-3)(3x-1)=x(3x-1)-3(3x-1)
=x.3x+x.(-1)-3.3x-3.(-1)
=\(3x^2\)-1x-9x+3
=\(3x^2\)+(-1x-9x)+3
=\(3x^2\)-10x+3
rút gọn biểu thức
A) \(x^2\)-(x+4)(x-1)=\(x^2\)- x(x-1)-4(x-1)
=\(x^2\)-x.x-x.(-1)-4.x-4.(-1)
=\(x^2\)-\(x^2\)+1x-4x+4
=(\(x^2-x^2\))+(1x-4x)+4
= -3x+4
B) x(x+2)-(x-2)(x+4)=x.x+x.2-x(x+4)+2(x+4)
=\(x^2+2x\)-x.x-x.4+2.x+2.4
=\(x^2+2x-x^2-4x+2x+8\)
=(\(x^2-x^2\))+(2x-4x+2x)+8
=8
tính giá trị biểu thức
A=3(x-2)-(2+x)(x-3)
=3.x+3.(-2)-2(x-3)-x(x-3)
=3x-6-2.x-2.(-3)-x.x-x(-3)
=3x-6-2x+6-\(x^2\)+3x
=(3x-2x+3x)+(-6+6)\(-x^2\)
=4x - \(x^2\)
thay x=-8 vào biểu thức thu gọn ta được:
4.(-8)- (-8)\(^2\)
= - 32 +64
= 32
B= x(3-x)-(1+x)(1-x)
=x.3+x.(-x)-1(1-x)-x(1-x)
=3x -\(x^2\)-1.1-1 .(-x)-x.1-x.(-x)
=3x\(-x^2\)-\(1^2\)+1x-1x+\(x^2\)
=(3x+1x-1x)+(\(-x^2+x^2\))-1
=3x-1
thay x=-5 vào biểu thức thu gọn ta được:
3.(-5)-1
=-15-1
=-16
Thu gọn biểu thức
4) (3x - 2) (x - 3)
= ( 3x2 - 2x ) - ( 3x x 3 - 2 x 3 )
= 3x2 - 2x - 3x x 3 + 2 x 3
= 3x2 - 2x - 9x + 6
= 3x2 - 11x + 6
5) (2x + 1) (x + 3)
= ( 2x2 + 1x ) + ( 6x + 3 )
= 2x2 + 1x + 6x + 3
= 2x2 + 7x + 3
6) (x - 3) (3x - 1)
= ( 3x2 - 9x ) - ( x - 3 )
= 3x2 - 9x - x + 3
= 3x2 - 10 + 3
Rút gọn biểu thức
A) x^2 - (x + 4) (x - 1)
= x2 - ( x2 + 4x ) - ( x + 4 )
= x2 - x2 - 4x - x - 4
= -5x - 4
B) x (x + 2) - (x - 2) (x + 4)
= x2 + 2x - ( x2 - 2x ) + ( 4x - 8 )
= x2 + 2x - x2 + 2x + 4x - 8
= 8x - 8
Tính giá trị biểu thức
A = 3 (x - 2) - (2 + x) (x - 3) tại x = - 8
Thế x = -8 vào, ta có :
= 3 ( -8 -2 ) - ( 2 + -8 ) ( -8 - 3 )
= 3 x ( -10 ) - ( - 6 ) ( -11 )
= -30 - 66
= -96
B = x (3 - x) - (1 + x) ( 1 - x) tại x = - 5
Thế x = - 5 vào, ta có :
= -5 ( 3 - -5 ) - ( 1+ -5 ) ( 1 - -5 )
= -5 x 8 - (-4) x 6
= - 40 - -24
= -40 + 24
= -16
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hok tốt nha
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(x-1)/2015 + x/2014 + 1/503 - (x-3)/2013 - x/2012 - 1/1007 =0
(x-2016)/2015 + (x-2016)/2014 - (x-2016)/2012 - (x-2016)/2013 = 0
(x-2016) ( 1/2015 + 1/2016 - 1/2013 - 1/2012) = 0
Mà 1/2015 + 1/2016 - 1/2013 - 1/2012 khác 0
Suy ra x -2016=0
x=2016
Chỗ nào thắc mắc nhớ hỏi mik nhe!