Prove that (1/x + 1/y + 1/z) is greater than 3
21:39
a * b = ab + a + b
14:38
Find all real pairs (x,y)
16:47
Prove that n^3 +11n is divisible by 6
16:54
An integral with a classic result
3:46
Harder than it looks!
9:29
If x^y=8 and x is bigger than 1, then what's the minimum of x+y=?
14:53
Find all x
18:11