Đáp án:
Giải thích các bước giảỉ:
bài 5:
b) a² +b² -c² -d²-2ab +2cd
=(a² -2ab +b²) -( c² -2cd +d²)
=(a -b)² -(c -d)²
=(a -b -c +d).(a -b +c -d)
d)x² .(y -z) +y²(z -x)+z²(x -y)
=x²y -x²z +y²z -xy² +z²(x -y)
=(x²y -xy²) -(x²z -y²z) +z² (x-y)
=xy.(x -y) -z.(x² -y²) +z²(x-y)
=xy.(x -y) -x.(x +y).( x -y) +z²(x -y)
=(x -y) .[ xy -x.(x +y) +z²]
=(x -y).[ xy -x² -xy +z²]
=(x -y) .(z²-x²)
=(x -y).(x +z).(z -x)
f)$x^{12}$ -3$x^{6}$ $y^{6}$ +2$y^{12}$
=$x^{12}$ -$x^{6}$ $y^{6}$ -2$x^{6}$ $y^{6}+$2$y^{12}$
=($x^{12}$ -$x^{6}$ $y^{6}$) -( 2$x^{6}$ $y^{6}-$2$y^{12}$ )
=$x^{6}$($x^{6}$ - $y^{6}$) -2$y^{6}$( $x^{6}$ -$y^{6}$ )
=( $x^{6}$ -$y^{6}$ ).( $x^{6}$ -2$y^{6}$
h) (x -8)² -784
=(x -8)² -28²
=(x -8 -28).(x -8 +28)
=(x -36).(x +20)
