\(A=1+5^2+5^3+...+5^{2015}+5^{2016}\)

\(5A=5+5^3+5^4+...+5^{2016}+5^{2017}\)

\(4A=\left(5+5^3+5^4+...+5^{2016}+5^{2017}\right)-\left(1+5^2+5^3+...+5^{2015}+5^{2016}\right)\)

\(=5+5^{2017}-\left(1+5^2\right)\)

\(=4+5^{2017}-5^2\)

\(A=\frac{4+5^{2017}-5^2}{4}\)

Ta có : 5A = 5 + 5^3 + 5^4 + ... + 5^2016 + 5^2017

  =>    5A - A = ( 5 + 5^3 + 5^4 + ... + 5^2016 + 5^2017 ) - ( 1 + 5^2 + 5^3 + ... + 5^2015 + 5^2016 )

  =>         4A = 4 + 5^2 + 5^2017

  =>           A = ( 4 + 5^2 + 5^2017 )/4

các bạn khác kq của mik

5^2017-1/4

7(x - 3) - x(3 - x)

= (x - 3)(7 + x)

chỉ bt có v mà k bt có đúng k 

1 ) 7 ( x - 3 ) - x ( 3 - x ) 

= 7 ( x - 3 ) + x ( x - 3 )

= ( x - 3 ) ( 7 + x )

2 ) 4x² - 6x + 3 - 2x

= 4x² - 2x - 6x + 3

= 2x ( 2x - 1 ) - 3 ( 2x - 1 )

= ( 2x - 1 ) ( 2x - 3 )

3 ) ( 4 - x ) - 4x + x²

= ( 4 - x ) - x ( 4 - x )

= ( 4 - x ) (  1 - x )

4 ) x² - 2xy + y²

= ( x - y )²

1, \(7\left(x-3\right)-x\left(3-x\right)=7\left(x-3\right)+x\left(x-3\right)\)

\(=\left(x-3\right)\left(x+7\right)\)

2,\(4x^2-6x+\left(3-2x\right)=4x^2-8x+3\)

\(=4x^2-6x-2x+3=2x\left(2x-3\right)-\left(2x-3\right)\)

\(=\left(2x-3\right)\left(2x-1\right)\)

3,\(\left(4-x\right)-4x+x^2=x^2-5x+4\)

\(=x^2-x-4x+4=x\left(x-1\right)-4\left(x-1\right)=\left(x-1\right)\left(x-4\right)\)

4,\(x^2-2xy+y^2=\left(x-y\right)^2\)

B1:

a,\(\left(3x-2\right)\left(x-3\right)=3x^2-9x-2x+6=3x^2-11x+6\)

b,\(\left(2x+1\right)\left(x+3\right)=2x^2+6x+x+3=2x^2+7x+3\)

c,\(\left(x-3\right)\left(3x-1\right)=3x^2-x-9x+3=3x^2-10x+3\)

B2:

1)\(x^2-\left(x+4\right)\left(x-1\right)=x^2-\left(x^2-x+4x-4\right)=x^2-x^2+x-4x+4=-3x+4\)

2)\(x\left(x+2\right)-\left(x-2\right)\left(x+4\right)=x^2+2x-\left(x^2+4x-2x-8\right)\)

\(=x^2+2x-x^2-4x+2x+8=8\)

dễ mak

Bài 1 :

1) a² - 4 + y ( a - 2 )

= ( a + 2 ) ( a - 2 ) + y ( a - 2 )

= ( a - 2 ) ( a + 2 + y )

2) ( x - 2 )² - 9y²

= ( x - 2 - 3y ) ( x - 2 + 3y )

Bài 2 :

1) 3 ( x + 4 ) - 2x = 5

=> 3x + 12 - 2x = 5

=> x + 12 = 5

=> x = 5 - 12 = - 7

Vậy x = - 7

2) x ( x - 2 ) - x² - 6 = 0

=> x² - 2x - x² - 6 = 0

=> - 2x - 6 = 0

=> 2x = - 6

=> x = \(-\frac{6}{2}=3\)

Vậy x = 3

3 ) x² - 3x = 0

=> x ( x - 3 ) = 0

=> \(\orbr{\begin{cases}x=0\\x-3=0\end{cases}}\)

=> \(\orbr{\begin{cases}x=0\\x=3\end{cases}}\)

Vậy \(x\in\left\{0;3\right\}\)

4) 5 - 3 ( x - 6 ) = 4

=> 5 - 3x + 18 = 4

=> 3x = 5 + 18 - 4

=> 3x = 19

=> x = \(\frac{19}{3}\)

Vậy \(x=\frac{19}{3}\)

Thanks nhìu nha😍😍😍😍

Mik sẽ k cho bạn đó mik viết nhầm

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

100% đúng 

hok tốt nha 

\(=\left(x^3-2x^2+x+2x^2-4x+2-2x+7\right):\left(x^2-2x+1\right)\\ =\left[\left(x^2-2x+1\right)\left(x+2\right)-2x+7\right]:\left(x^2-2x+1\right)\\ =x+2\left(dư:-2x+7\right)\)