Function does not returns value

What is wrong here? Function Tst1 does not return the new value of x.

It should be 6 but, x is still 1???

Thank you for any help.

function Tst2()

{

x = 1;

Tst1(x);

}

// ======================

function Tst1(x)

{

x = x + 5;

return x;

}