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

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

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

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