b)-x^3+12x^2-48x+46

  =-(x^3-12x^2+48x-46)

  =-(x^3-3x^2.4+3x4^2-4^3)

  =-(x-4)^3

c: \(\dfrac{1}{8}x^3-\dfrac{9}{4}x^2y+\dfrac{27}{2}xy^2-27y^3=\left(\dfrac{1}{2}x-3y\right)^3\)

\(a,=\left(3x+2y\right)^3\\ b,=\left(4-x\right)^3\\ c,=\left(\dfrac{1}{2}x-3y\right)^3\)

A) \(x^3+27\)

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

\(=\left(x+3\right)\left(x^2-3x+9\right)\)

B) \(x^3-\dfrac{1}{8}\)

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

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

C) \(8x^3+y^3\)

\(=\left(2x\right)^3+y^3\)

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

D) \(8x^3-27y^3\)

\(=\left(2x\right)^3-\left(3y\right)^3\)

\(=\left(2x-3y\right)\left(4x^2+6xy+9y^2\right)\)

a)\(\left(x+3\right)\left(x^2-3x+9\right)\)

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

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

d)\(\left(2x-3y\right)\left(4x^2+6xy+9y^2\right)\)

\(a,=\left(x+3\right)^3=\left(7+3\right)^3=10^3=1000\\ b,=\left(4-x\right)^3=\left(4-24\right)^3=\left(-20\right)^3=-8000\\ c,=\left(x-1\right)^3=\left(11-1\right)^3=10^3=1000\)

2^n/32 = 4 => 2^n = 4 . 32 = 128 => n =7

27^n . 9^n = 9^27 . 81 

=> (27.9)^n = 9^27 . 9^2

=> 243^n = 9^54

=> 243^n = 243^1458

vay n=1458

1/9 . 3^4 . 3^n+1 = 9^4

=> 9 . 3^n+1 = 6561

=> 3^n+1 = 6561 /9

=> 3^n+1 = 729

=> n = 5

\(a.\frac{2^n}{32}=4\Rightarrow2^n=32.4=128=2^7\Rightarrow n=7\)

\(b.27^{n^{ }}.9^n=9^{27}:81\Rightarrow3^{3n}.3^{2n}=3^{54}:3^4\)

\(\Rightarrow3^{5n}=3^{50}\Rightarrow n=50:5=10\)

\(c.\frac{1}{9}.3^4.3^{n+1}=9^4\Rightarrow\frac{1}{3^2}.3^4.3^{n+1}=3^8\)

\(\Rightarrow3^2.3^{n+1}=3^8\Rightarrow3^{n+1}=3^6\Rightarrow n=6-1=5\)

a, 2xy^2 ( x^3 -3xy - 4 )

b, x^2 - 4x - 4x +16

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

= (x-4) (x-4)

Lời giải:

a.

$2x^4y^2-6x^2y^3-8xy^2=2xy^2(x^3-3xy-4)$

b. 

$x^2-8x+16=x^2-2.4.x+4^2=(x-4)^2$

c.

$12x^2-12=12(x^2-1)=12(x-1)(x+1)$

d. 

$5x^2y-20xy+20y=5y(x^2-4x+4)=5y(x-2)^2$
e.

$3x^2y^2-27y^2=3y^2(x^2-9)=3y^2(x-3)(x+3)$

f. 

$8x^3-27y^3=(2x)^3-(3y)^3=(2x-3y)(4x^2+6xy+9y^2)$

g.

$4x^4-8x^3+4x^2=(2x^2)^2-2.2x^2.2x+(2x)^2$

$=(2x^2-2x)^2=[2x(x-1)]^2=4x^2(x-1)^2$
h.

$7x^2y^2-28y^4=7y^2(x^2-4y^2)=7y^2(x-2y)(x+2y)$

$

a: \(8x^3-1=\left(2x-1\right)\left(4x^2+2x+1\right)\)

b: \(x^3+8y^3=\left(x+2y\right)\left(x^2-2xy+4y^2\right)\)

c: \(x^3+125=\left(x+5\right)\left(x^2-5x+25\right)\)

d: \(x^3-27y^3=\left(x-3y\right)\left(x^2+3xy+9y^2\right)\)

a) 8x³ - 1

= (2x)³ - 1³

= (2x - 1)(4x² + 2x + 1)

b) x³ + 8y³

= x³ + (2y)³

= (x + 2y)(x² + 2xy + 4y²)

c) x³ + 125

= x³ + 5³

= (x + 5)(x² - 5x + 25)

d) x³ - 27y³

= x³ - (3y)³

= (x - 3y)(x² + 3xy + 9y²)

 Chúc bạn học tốt

a. 8x³ - 1

⇔ (2x)³ - 1³

⇔ (2x - 1)³.

b. x³ + 8y³

⇔ x³ + (2y)³

⇔ (x + 2y)³

c. x³ + 125

⇔ x³ + 5³

⇔ (x + 5)³

d. x³ - 27y³

⇔ x³ - (3y)³

⇔ (x - 3y)³

a)8x3 + * + * + 27y3 = (* + *)3

=>A=(2x+3y)^3

b) (2x+1)^3

c)(x-2y)^3

d)(3x-2)(3x+2)

e)(3x-1)(9x^2+3x+1)

f)....................

6: \(27x^3+1=\left(3x+1\right)\left(9x^2-3x+1\right)\)

7: \(\left(2x+1\right)^2=4x^2+4x+1\)

8: \(\left(2x-1\right)^2=4x^2-4x+1\)

9: \(9-16x^2=\left(3-4x\right)\left(3+4x\right)\)

2S=2/1.2.3+2/2.3.4+...+2/8.9.10

2S=1/1.2+1/2.3+1/3.4+1/4.5+....+1/8.9+1/9.10

2S=1-1/2+1/2-1/3+1/3-1/4+...+1/9-1/10

2S=1-1/10

2S=9/10

S=9/10:2

S=9/10.2

S=9/20