a) 4 x 5 - 4 x 2 + 4

= 4 x 5 - 4 x 2 + 4 x 1

= 4 x ( 5 - 2 + 1 )

= 4 x 4

= 16

b) 2 x 3 + 9 + 3 x 3

= 2 x 3 + 3 x 3 + 3 x 3

= 3 x ( 2 + 3 + 3 )

= 3 x 8

= 24

c) 2 + 2 x 9

= 2 x 1 + 2 x 9

= 2 x ( 1 + 9 )

= 2 x 10

= 20

a) 4 x 5 - 4 x 2 + 4

= 4 x 5 - 4 x 2 + 4 x 1

= 4 x ( 5 - 2 + 1 )

= 4 x 4

= 16

b) 2 x 3 + 9 + 3 x 3

= 2 x 3 + 3 x 3 + 3 x 3

= 3 x ( 2 + 3 + 3 )

= 3 x 8

= 24

c) 2 + 2 x 9

= 2 x 1 + 2 x 9

= 2 x ( 1 + 9 )

= 2 x 10

= 20

Đáp án đây nhé 

\(A=\dfrac{5x_1-x_2}{x_1}+\dfrac{5x_2-x_1}{x_2}\)

\(=\dfrac{5x_1\cdot x_2-x_2^2+5x_1x_2-x_1^2}{x_1x_2}\)

\(=\dfrac{10x_1x_2-\left[\left(x_1+x_2\right)^2-2x_1x_2\right]}{x_1x_2}\)

\(=\dfrac{10\cdot4-\left[5^2-2\cdot4\right]}{4}=\dfrac{40-25+8}{4}=\dfrac{23}{4}\)

bằng 10

\(A=x^5-5x^4+5x^3-5x^2+5x\)

\(=x^5-\left(x+1\right)x^4+\left(x+1\right)x^3-\left(x+1\right)x^2+\left(x+1\right)x\)

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

\(=x\)

\(=4\)

  2x1=2     3x1=3     4x1=4      5x1=5     2:2= 1     3:3= 1    4:4=1    5:5=1

   2x2= 4    3x2=6     4x2= 8     5x2=10     4:2=   2   6:3= 2     8:4=2    10:5=2

   2x3=6     3x3= 9    4x3=12      5x3=15     6:2=3      9:3= 3     12:4=3  15:5=3

   2x4=8    3x4=12     4x4=16      5x4=20     8:2=4      12:3=4    16:4=4  20:5=4

   2x5=10     3x5= 15    4x5= 20     5x5= 25    10:2=5   15:3=  5  20:4=5  25:5=5

   2x6=12     3x6=18     4x6= 24     5x6=30     12:2=6    18:3= 6   24:4=6  30:5=6

   2x7= 14    3x7=21     4x7= 28     5x7=35     14:2=7    21:3=7    28:4=7  35:5=7

   2x8=16     3x8=24     4x8= 32     5x8=50     16:2=8    24:3=8    32:4=8  40:5=8

   2x9= 18    3x9= 27    4x9= 36     5x9=45     18:2=9    27:3= 9   36:9=9  45:5=9

   2x10=20   3x10=30   4x10= 40   5x10=50   20:2=10    30:3=10    40:4= 10 50:5=10

b: \(\left(x^2+10x+8\right)^2-\left(8x+4\right)\left(x^2+8x+7\right)\)

\(=\left\lbrack\left(x^2+8x+7\right)+\left(2x+1\right)\right\rbrack^2-4\left(2x+1\right)\left(x^2+8x+7\right)\)

\(=\left(x^2+8x+7\right)^2+2\left(x^2+8x+7\right)\left(2x+1\right)+\left(2x+1\right)^2-4\left(2x+1\right)\left(x^2+8x+7\right)\)

\(=\left(x^2+8x+7\right)^2-2\left(x^2+8x+7\right)\left(2x+1\right)+\left(2x+1\right)^2\)

\(=\left(x^2+8x+7-2x-1\right)^2=\left(x^2+6x+6\right)^2\)

d: \(B=x^4+4x^3+8x^2+8x+4\)

\(=x^4+2x^3+2x^2+2x^3+4x^2+4x+2x^2+4x+4\)

\(=x^2\left(x^2+2x+2\right)+2x\left(x^2+2x+2\right)+2\left(x^2+2x+2\right)\)

\(=\left(x^2+2x+2\right)\left(x^2+2x+2\right)=\left(x^2+2x+2\right)^2\)

e: \(C=x^4-2x^3+5x^2-4x+4\)

\(=x^4-x^3+2x^2-x^3+x^2-2x+2x^2-2x+4\)

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

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

1: \(=x^2+1\)

3: \(=\left(x-y-z\right)^2\)

5 x 1 = 5

5 x 2 = 10

5 x 3 = 15

k mik nha bn

thank you very much

5x1=5

5x2=10

5x3=15

TK MÌNH NHÉ , THANK 

CHÚC BẠN NĂM MỚI VUI VẺ , HỌC GIỎI , HẠNH PHÚC

6: \(\left(2x^3-5x^2+6x-15\right):\left(2x-5\right)\)

\(=\frac{x^2\left(2x-5\right)+3\left(2x-5\right)}{2x-5}\)

\(=\frac{\left(2x-5\right)\left(x^2+3\right)}{2x-5}=x^2+3\)

2: \(\frac{2x^4-5x^2+x^3-3-3x}{x^2-3}\)

\(=\frac{2x^4-6x^2+x^3-3x+x^2-3}{x^2-3}\)

\(=\frac{2x^2\left(x^2-3\right)+x\cdot\left(x^2-3\right)+\left(x^2-3\right)}{x^2-3}=2x^2+x+1\)

5: \(\left(2x^3+5x^2-2x+3\right):\left(2x^2-x+1\right)\)

\(=\frac{2x^3-x^2+x+6x^2-3x+3}{2x^2-x+1}=\frac{\left(2x^2-x+1\right)\left(x+3\right)}{2x^2-x+1}\)

=x+3

3: \(\left(x-y-z\right)^5:\left(x-y-z\right)^3=\left(x-y-z\right)^{5-3}=\left(x-y-z\right)^2\)

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

\(=\frac{x^2\left(x-3\right)+\left(x-3\right)}{x-3}=x^2+1\)

1: Sửa đề: 3x-5

\(=\dfrac{-x^2\left(3x-5\right)-3\left(3x-5\right)}{3x-5}=-x^2-3\)

2: \(=\dfrac{5x^4-5x^3+14x^3-14x^2+12x^2-12x+8x-8}{x-1}\)

=5x^2+14x^2+12x+8

3: \(=\dfrac{5x^3+10x^2+4x^2+8x+4x+8}{x+2}=5x^2+4x+4\)

4: \(=\dfrac{\left(x^2-1\right)\left(x^2+1\right)-2x\left(x^2-1\right)}{x^2-1}=x^2+1-2x\)

5: \(=\dfrac{x^2\left(5-3x\right)+3\left(5-3x\right)}{5-3x}=x^2+3\)