Question

Phân tích đa thức thành nhân tử

Answer 1

13.

$25-x^2+4xy-4y^2=25-(x^2-4xy+4y^2)$

$=5^2-(x-2y)^2=(5-x+2y)(5+x-2y)$

14.

$4x^2+4xy+y^2-9=(4x^2+4xy+y^2)-3^2$

$=(2x+y)^2-3^2=(2x+y-3)(2x+y+3)$
15.

$x^2+4xy-16+4y^2=(x^2+4xy+4y^2)-16$

$=(x+2y)^2-4^2=(x+2y-4)(x+2y+4)$

Answer 2

16.

$4x^2-4x+1-y^2-8y-16=(4x^2-4x+1)-(y^2+8y+16)$
$=(2x-1)^2-(y+4)^2=(2x-1-y-4)(2x-1+y+4)$

$=(2x-y-5)(2x+y+3)$

17.

$x^2-2xy+y^2-z^2+2zt-t^2$

$=(x^2-2xy+y^2)-(z^2-2zt+t^2)$

$=(x-y)^2-(z-t)^2=(x-y-z+t)(x-y+z-t)$

18.

$(x+y)^2-2(x+y)+1$

$=(x+y-1)^2$