Đáp án:
a, $\dfrac{2yz^2}{3x}$
b, $\dfrac{3}{10}$
Giải thích các bước giải:
a, $\dfrac{18x^2y^2}{15z}\cdot\dfrac{5z^3}{9x^3y}$
$=\dfrac{18.5.x^2y^2z^3}{15.9.x^3yz}$
$=\dfrac{2yz^2}{3x}$
b, $\dfrac{5x+5y}{4x-4y}\cdot\dfrac{6x-6y}{25x+25y}$
$=\dfrac{5(x+y)}{4(x-y)}\cdot\dfrac{6(x-y)}{25(x+y)}$
$=\dfrac{3}{2.5}$
$=\dfrac{3}{10}$