Đáp án:
$9)\\ c)Q=8\\ 10)\\ a)140608\\ b)124251499\\ c)125000\\ d)999$
Giải thích các bước giải:
$9)\\ c)Q=\left(\dfrac{x}{y}+1\right)^3-15\left(\dfrac{x+y}{y}\right)^2+75\left(\dfrac{x-y}{y}+2\right)-125\\ =\left(\dfrac{x}{y}+1\right)^3-15\left(\dfrac{x}{y}+1\right)^2+75\left(\dfrac{x}{y}+1\right)-125\\ =\left(\dfrac{x}{y}+1\right)^3-3.\left(\dfrac{x}{y}+1\right)^2.5+3.\left(\dfrac{x}{y}+1\right)-5^3\\ =\left(\dfrac{x}{y}+1-5\right)^3\\ =\left(\dfrac{x}{y}-4\right)^3\\ x=12; y=2; Q=\left(\dfrac{12}{2}-4\right)^3\\ =(6-4)^3\\ =2^3\\ =8\\ 10)\\ a)52^3\\ =(50+2)^3\\ =50^3+3.50^2.2+3.50.2^2+2^3\\ =5^3.10^3+3.5^2.10^2.2+3.50.2^2+2^3\\ =125000+15000+600+8\\ =140608\\ b)499^3\\ =(500-1)^3\\ =500^3-3.500^2.1+3.500.1^2-1^3\\ =5^3.100^3-3.5^2.100^2+3.500-1\\ =125000000-750000+1500-1\\ =124251499\\ c)48^3+6.48^2+12.48+8\\ =48^3+3.48^2.2+3.48.2^2+2^3\\ =(48+2)^3\\ =50^3\\ =5^3.10^3\\ =125000\\ d)12^3-6.12^2+144-9\\ =12^3-3.12^2.2+3.12.2^2-2^3-1\\ =(12-2)^3-1\\ =10^3-1\\ =999$
