Đáp án:
Giải thích các bước giải:
$a,49(y-4)^2-9(y+2)^2$
$=(7y-28)^2-(3y+6)^2$
$=(7y-28-3y-6)(7y-28+3y+6)$
$=(4y-34)(10y-22)$
$=4(2y-17)(5y-11)$
$b,\left (2x+\dfrac{1}{3} \right)\left (4x^2-\dfrac{2x}{3}+\dfrac{1}{9} \right )$
$c,(5-x^2)(25+5x^2+x^4)$
$d,(x-y+5)^2-2(x-y+5)+1$
$=(x-y+5-1)^2$
$=(x-y+4)^2$
$e,(x^2+4y^2-5)^2-16(x^2y^2+2xy+1)$
$=(x^2+4y^2-5)^2-4^2(xy+1)^2$
$=(x^2+4y^2-5)^2-(4xy+4)^2$
$=(x^2+4y^2-5-4xy-4)(x^2+4y^2-5+4xy+4)$
$=(x^2-4xy+4y^2-9)(x^2+4xy+4y^2-1)$
$=(x-2y-3)(x-2y+3)(x+2y-1)(x+2y+1)$