\(4x^2+4x=80\Leftrightarrow4x^2+4x-80=0\)

\(\Leftrightarrow4x^2+4x+1-81=0\Leftrightarrow\left(2x+1\right)^2-9^2=0\)

\(\Leftrightarrow\left(2x-8\right)\left(2x+10\right)=0\Leftrightarrow x=4;x=-5\)

Trả lời:

\(4x^2+4x=80\)

\(\Leftrightarrow4x^2+4x-80=0\)

\(\Leftrightarrow4x^2+4x+1-81=0\)

\(\Leftrightarrow\left(4x^2+4x+1\right)-81=0\)

\(\Leftrightarrow\left(2x+1\right)^2-81=0\)

\(\Leftrightarrow\left(2x+1-9\right)\left(2x+1+9\right)=0\)

\(\Leftrightarrow\left(2x-8\right)\left(2x+10\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}2x-8=0\\2x+10=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=4\\x=-5\end{cases}}}\)

Vậy x = 4; x = - 5 là nghiệm của pt.

Không đăng các câu hỏi linh tinh lên diễn đàn nha bạn , không là bị ăn báo cáo đấy .

a, \(4x^4+81=\left(2x^2\right)^2+9^2=\left(2x^2\right)^2+36x^2+9^2-36x^2\)

\(=\left(2x^2+9\right)^2-\left(6x\right)^2=\left(2x^2-6x+9\right)\left(2x^2+6x+9\right)\)

b, \(64x^4+y^4=\left(8x^2\right)^2+\left(y^2\right)^2=\left(8x^2\right)^2+16x^2y^2+\left(y^2\right)^2-16x^2y^2\)

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

thank bn nha 

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

7, \(10ax-5ay-2x+y=5a\left(2x-y\right)-\left(2x-y\right)=\left(5a-1\right)\left(2x-y\right)\)

8, xem lại đề bạn nhé

9, \(4x^2-y^2+8y-16=4x^2-\left(y^2-8y+16\right)=4x^2-\left(y-4\right)^2\)

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

Trả lời:

6, x²y + xy² - 4x - 4y = ( x²y + xy² ) - ( 4x + 4y ) = xy ( x + y ) - 4 ( x + y ) = ( x + y )( xy - 4 )

7, 10ax - 5ay - 2x + y = ( 10ax - 5ay ) - ( 2x - y ) = 5a ( 2x - y ) - ( 2x - y ) = ( 2x - y )( 5a - 1 ) 

8, Sửa đề: x³ - 2x² + 2x - 4 = ( x³ - 2x² ) + ( 2x - 4 ) = x² ( x - 2 ) + 2 ( x - 2 ) = ( x - 2 )( x² + 2 )

9, 4x² - y² + 8y - 16 = 4x² - ( y² - 8y + 16 ) = 4x² - ( y - 4 )² = ( 2x - y + 4 )( 2x + y - 4 )

1, \(x^2\left(x-3\right)-4x+12=x^2\left(x-3\right)-4\left(x-3\right)\)

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

2, \(2a\left(x+y\right)-x-y=2a\left(x+y\right)-\left(x+y\right)=\left(2a-1\right)\left(x+y\right)\)

3, \(2x-4+5x^2-10x=2\left(x-2\right)+5x\left(x-2\right)=\left(2+5x\right)\left(x-2\right)\)

4, sửa đề : 

 \(6x^2-12x-7x+14=6x\left(x-2\right)-7\left(x-2\right)=\left(6x-7\right)\left(x-2\right)\)

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

a) x²(x-3)-4x+12

=x²(x-3)-4(x-3)

=(x-3)(x²-4)

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

b) 2a(x+y)-x-y

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

=(x+y)(2a-1)

c) 2x-4+5x²-10x

=2(x-2)+5x(x-2)

=(x-2)(2+5x)

d) 5x²-12x-7x+14

=5x²-19x+14

e) xy-y²-3x+3y

=y(x-y)-3(x-y)

=(x-y)(y-3)

#H

\(3\left(1-4x\right)\left(x-1\right)+4\left(3x-2\right)\left(x+3\right)=-27\)

\(\Leftrightarrow3\left(-1-4x^2+5x\right)+4\left(3x^2+7x-6\right)=-27\)

\(\Leftrightarrow-12x^2+15x-3+12x^2+28x-24=-27\)

\(\Leftrightarrow43x-27=-27\Leftrightarrow x=0\)

\(3\left(1-4x\right)\left(x-1\right)+4\left(3x-2\right)\left(x+3\right)=-27\)

\(\Leftrightarrow\left(3-12x\right)\left(x-1\right)+\left(12x-8\right)\left(x+3\right)=-27\)

\(\Leftrightarrow3x-3-12x^2+12x+12x^2+36x-8x-24+27=0\)

\(\Leftrightarrow43x=0\)

\(\Leftrightarrow x=0\)

#H

Trả lời:

21, ( a + 1 )³ = a³ + 3a² + 3a + 1

22, ( a + 2 )³ = a³ + 3.a².2 + 3.a.2² + 2³ = a³ + 6a² + 12a + 8

23, ( x + 1 )³ = x³ + 3x² + 3x + 1

24, ( x + 2 )³ = x³ + 3.x².2 + 3.x.2² + 2³ = x³ + 6x² + 12x + 8

25, ( x + 3 )³ = x³ + 3.x².3 + 3.x.3² + 3³ = x³+ 9x² + 27x + 27

26, ( x + 4 )³ = x³ + 3.x².4 + 3.x.4² + 4³ = x³ + 12x² + 48x + 64

27, ( 2x + 3y )³ = (2x)³ + 3.(2x)².3y + 3.2x.(3y)² + (3y)³ = 8x³ + 36x²y + 54xy² + 27x³

28, ( 3x + 1 )³ = (3x)³ + 3.(3x)².1 + 3.3x.1² + 1³ = 27x³ + 27x² + 9x + 1

29, ( 5x + 1 )³ = (5x)³ + 3.(5x)².1 + 3.5x.1² + 1³ = 125x³ + 75x² + 15x + 1

30, ( 4x + 2y )³ = (4x)³ + 3.(4x)².2y + 3.4x.(2y)² + (2y)³ = 64x³ + 96x²y + 48xy² + 8y³

31, ( a - 1 )³ = a³ - 3a² + 3a - 1

32, ( a - 2 )³ = a³ - 3.a².2 + 3.a.2² - 2³ = a³ - 6a² + 12a - 8

33, ( x - 3 )³ = x³ - 3.x².3 + 3.x.3² - 3³ = x³ - 9x² + 27x - 27

34, ( x - 4 )³ = x³ - 3.x².4 + 3.x.4² - 4³ = x³ - 12x² + 48x - 64

35, ( x - 5 )³ = x³ - 3.x².5 + 3.x.5² - 5³ = x³ - 15x² + 75x - 125

36, ( 2x - 3y )³ = (2x)³ - 3.(2x)².3y + 3.2x.(3y)² - (3y)³ = 8x³ - 36x² + 54x - 27x³

37, ( x² - 2y )³ = (x²)³ - 3.(x²)².2y + 3.x².(2y)² - (2y)³ = x⁶ - 6x⁴y + 12x²y² - 8y³

38, ( 2x² - 3y )³ = (2x²)³ - 3.(2x²)².3y + 3.2x².(3y)² - (3y)³ = 8x⁶ - 36x⁴y + 54x²y² - 27y³

39, ( 4 - 4y² )³ = 4³ - 3.4².4y² + 3.4.(4y²)² - (4y²)³ = 64 - 48y² + 192y⁴ - 64y⁶

40, ( 3x² - 2y² )³ = (3x²)³ - 3.(3x²)².2y² + 3.3x².(2y²)² - (2y²)³ = 27x⁶ - 54x⁴y² + 36x²y⁴ - 8y⁶ 

a, \(a^4+64=\left(a^2\right)^2+8^2=\left(a^2\right)^2+16a^2+8^2-16a^2\)

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

b, \(a^4+4b^2=\left(a^2\right)^2+\left(2b\right)^2=\left(a^2\right)^2+4a^2b+4b^2-4a^2b\)ĐK : b >= 0 

\(=\left(a+2b\right)^2-\left(2a\sqrt{b}\right)^2=\left(a+2b-2a\sqrt{b}\right)\left(a+2b+2a\sqrt{b}\right)\)

p/s : mình nghĩ phần b bạn nên để đề là \(a^4+4b^4\)sẽ hợp lí hơn 

Anh nhận bú lồn hoàn toàn miễn phí nha mấy em