Giải thích các bước giải:
a.$\dfrac{8x^3y-4x^2y}{4xy}+x^2+x=2x^2-x+x^2+x=3x^2$
b.$\dfrac{8x^3y^4-12x^4y^3}{4x^2y^2-2xy^2}$
$=\dfrac{4x^3y^3(2y-3x)}{1y^2x(2x-1)}$
$=\dfrac{2x^2y(2y-3x)}{2x-1}$
c.$x^2-2xy+y^2-25=(x-y)^2-5^2=(x-y-5)(x-y+5)$
d.$5x(x-3)=5x^2+7x-5$
$\to 5x^2-15x=5x^2+7x-5$
$\to 22x=5$
$\to x=\dfrac{5}{22}$
e.$9x^2-(x-4)^2=0$
$\to (3x-x+4)(3x+x-4)=0$
$\to (2x+4)(4x-4)=0$
$\to x\in\{1,-2\}$