\(x(x^2+x+1)=4^y-1 \) với x,y nguyên dương

\((x+10)(\dfrac{720}{x}-6)=720\) (ĐK: 
⇔\(720x-6x^2+7200-60x=720x\) 

⇔\((x-30)(x+40)=0\)

⇔\(\left[\begin{array}{} x-30=0\\ x+40=0 \end{array} \right.\)⇔\(\left[\begin{array}{} x=30\\ x=40 \end{array} \right.\)

Vậy  .
 

bài nào???

\(Cho a,b,c>0. Cmr: \dfrac{a^3b}{1+ab^2}+\dfrac{b^3c}{1+bc^2}+\dfrac{c^3a}{1+ca^2}>\dfrac{abc(a+b+c)}{1+abc}\)