a. 3x² + 6xy + 3y ² b.5x+5y-x²-2xy-y ² c. (x-2y)³-(x+2y)(x²-2xy+4y²)+6x²y d.x²-y²-4x+4
2 câu trả lời
a)3x² + 6xy + 3y²
=3(x²+2xy+y²)
=3$(x+y)^{2}$
b)5x+5y-x²-2xy-y²
=5(x+y)-(x²+2xy+y²)
=5(x+y)-$(x+y)^{2}$
=(x+y)(5-x-y)
c) (x-2y)³-(x+2y)(x²-2xy+4y²)+6x²y
=$x^{3}$- $6x^{2}$y+12x$y^{2}$-$8y^{3}$ -($x^{3}$+$8y^{3}$)+6x²y
=$x^{3}$- $6x^{2}$y+12x$y^{2}$-$8y^{3}$ -$x^{3}$-$8y^{3}$+6x²y
=12x$y^{2}$-$8y^{3}$-$8y^{3}$
=12x$y^{2}$-$16y^{3}$
=4$y^{2}$(3x-4y)
d)x²-y²-4x+4
=x²-4x+4-y²
=$(x-2)^{2}$-y²
=(x-2-y)(x-2+y)