Sửa đề : \(9\left(x+y-1\right)^2-4\left(2x+3y+1\right)^2\)
\(=\left(9x+9y-9\right)^2-\left(8x+12y+4\right)^2\)
\(=\left(9x+9y-9-8x-12y-4\right)\left(9x+9y-9+8x+12y+4\right)\)
\(=\left(x-3y-13\right)\left(17x+21y-5\right)\)
Đúng là Tú có khác (:
9( x + y - 1 )2 - 4( 2x + 3y + 1 )2
= 32( x + y - 1 )2 - 22( 2x + 3y + 1 )2
= [ 3( x + y - 3 ) ]2 - [ 2( 2x + 3y + 1 ) ]2
= ( 3x + 3y - 3 )2 - ( 4x + 6y + 2 )2
= [ ( 3x + 3y - 3 ) - ( 4x + 6y + 2 ) ][ ( 3x + 3y - 3 ) + ( 4x + 6y + 2 ) ]
= ( 3x + 3y - 3 - 4x - 6y - 2 )( 3x + 3y - 3 + 4x + 6y + 2 )
= ( -x - 3y - 5 )( 7x + 9y - 1 )
Ađu nhầm ((:, tuổi trẻ ai chẳng mắc sai lầm
\(9\left(x+y-1\right)^2-4\left(2x+3y+1\right)^2\)
\(=3^2\left(x+y-1\right)^2-2^2\left(2x+3y+1\right)^2\)
\(=\left(3x+3y-3\right)^2-\left(4x+6y+2\right)^2\)
\(=\left(3x+3y-3-4x-6y-2\right)\left(3x+3y-2+4x+6y+2\right)\)
\(=\left(-x-3y-5\right)\left(7x+9y-1\right)\)
c) 2x2(x +1) + 4x(x +1); d) 2 x(y - 1) - 2