\(=\left(3x\right)^2-2\cdot3x\cdot4+4^2-1\)

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

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

\(=\left(3x-5\right)\left(3x-3\right)\)

1. (A+B)² = A²+2AB+B²

2. (A – B)²= A² – 2AB+ B²

3. A² – B²= (A-B)(A+B)

4. (A+B)³= A³+3A²B +3AB²+B³

5. (A – B)³ = A³- 3A²B+ 3AB²- B³

6. A³ + B³= (A+B)(A²- AB +B²)

7. A³- B³= (A- B)(A²+ AB+ B²)

8. (A+B+C)²= A²+ B²+C²+2 AB+ 2AC+ 2BC

* CHÚ Ý;

a/ a+b= -(-a-b)  ;   b/ (a+b)²= (-a-b)²   ;   c/  (a-b)²= (b-a)² ;   d/ (a+b)³= -(-a-b)³                              e/  (a-b)³=-(-a+b)³

(a+b)^2=a^2+2ab+b^2

(a-b)^2=a^2-2ab+b^2

a^2-b^2=(a+b)(a-b)

(a+b)^3=a^3+3a^2b+3ab^2+b^3

(a-b)^3=a^3-3a^2b+3ab^2-b^3

a^3+b^3=(a+b)(a^2-ab+b^2)

a^3-b^3=(a-b)(a^2+ab+b^2)

\(\left(a-x-y\right)^3-\left(a+x-y\right)^3\)

\(=\left[\left(a-x-y\right)-\left(a+x-y\right)\right]\left[\left(a-x-y\right)^2+\left(a-x-y\right)\left(a+x-y\right)+\left(a+x-y\right)^2\right]\)

\(=-2x.\left[a^2+x^2+y^2-2ax+2xy-2ay+\left(a-y\right)^2-x^2+a^2+x^2+y^2+2ax-2xy-2ay\right]\)

\(=-2x\left[a^2+x^2+y^2-2ax+2xy-2ay+a^2-2ay+y^2-x^2+a^2+x^2+y^2+2ax-2xy-2ay\right]\)

\(=-2x\left(3a^2+x^2+3y^2-4ay\right)\)

`(x+y+z)(x+y+z)`

`=(x+y+x)^2`

`=(x+y)^2(x+z)^2(z+y)^2`

Lời giải:
$(x+y+z)(x+y+z)=(x+y+z)^2=x^2+y^2+z^2+2(xy+yz+xz)$

Suy ra:4^3-12x+24x-12= 64 +12x-12

                                        = 12x+52

mk ko bik co dung ko sai thi thoi nha!

toi bạn rùi cmr là chết mày rùi

a² + b² + c² + d² + e² ≥ a(b + c + d + e) 

Ta có: a² + b² + c² + d² + e² 

= (a²/4 + b²) + (a²/4 + c²) + (a²/4 + d²) + (a²/4 + e²) 

Lại có: (a/2 - b)² ≥ 0 <=> a²/4 - ab + b² ≥ 0 <=> a²/4 + b² ≥ ab 

Tương tự ta có: 

. a²/4 + c² ≥ ac 
. a²/4 + d² ≥ ad 
. a²/4 + e² ≥ ae 

--> (a²/4 + b²) + (a²/4 + c²) + (a²/4 + d²) + (a²/4 + e²) ≥ ab + ac + ad + ae 

<=> a² + b² + c² + d² + e² ≥ a(b + c + d + e) --> đ.p.c.m 

Dấu " = " xảy ra <=> a/2 = b = c = d = e 

P/s: Hơi hơi dễ nhỉ

vu tuan hai la sao