Question

Are the numbers (2,3)(1,5)(2,7) a function ?

Answer 1

no

Explanation:

there are two coordinates with the same x value

Answer 2

Firstly they are not numbers, they are ordered pairs or points with a form
`(x,f(x))` yes they probably lie on a function graph but that would be rather impossible to find out. The function may be linear, exponential, logarithmic etc. we can't tell. All we can tell is that if these ordered pairs
`P_(1,2,3)` lie on a function graph
`P_(1,2,3)\in G_f` where
`G_f=\{(x,f(x)):\forall x\in D_f\wedge f(x)\in T_f\}` where D is definition set of function defined x's and T a transformation set of f(x)'s for this function. So yes they may lie on some lambda function but they themselves are nothing but an ordered pairs with no meaningful connection.

Hope this helps.