Products of four numbers would be positive if all 4 are positive or all 4 are negative or two are positive and 2 are negative
PPPP P 9C4/14C4 = 126/1001
NNNN P 5C4/14C14 = 5/1001
PPNN P 9C2*5C2/14C4 = 360/1001
"The gaming of numbers is called maths.So participate in this wonderful game and explore in it,learn in it and enjoy in it.Then only you can pass in this wonderful game."
Kumar Purnendu
If I feel unhappy, I do mathematics to become happy. If I am happy, I do mathematics to keep happy.