là 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999

Không có số tự nhien lớn nhất đâu nhé

Gọi vận tốc xe máy là x (km/h), vận tốc ô tô là x + 15 (km/h) theo đề bài ta có

\(\frac{90}{x}-\frac{90}{x+15}=0,5\)

\(\Leftrightarrow\orbr{\begin{cases}x=-60\left(l\right)\\x=45\end{cases}}\)

Nguy quá không biết chuyện gì sẩy ra, mình biết trên ô tô có 4 tên đầu gấu đuổi theo xe máy, 

Điều kiện: \(0\le x\le1\)

Đặt \(\sqrt{1-\sqrt{x}}=a\left(0\le a\le1\right)\)

\(\Rightarrow1-\sqrt{x}=a^2\)

\(\Leftrightarrow x=a^4-2a^2+1\)

Thế vào bài toán ta được

\(a^4-2a^2+1=\left(2005-a^2\right)\left(1-a\right)^2\)

\(\Leftrightarrow a^4-a^3-1003a^2+2005a-1002=0\)

\(\Leftrightarrow\left(a-1\right)^2\left(a^2+a-1002\right)=0\)

Vì \(0\le a\le1\)nên \(a^2+a-1002< 0\)

\(\Rightarrow a=1\)

\(\Leftrightarrow\sqrt{1-\sqrt{x}}=1\)

\(\Leftrightarrow x=0\)

@ Ali phân tích hàm bậc 4 hay thật.