Pretty simple because the first one is regularly used in languages like C and Java too and the second one actually is math-notation. Therefore,
1.
just means1.0
. In programming languages this is different from a simple1
which usually means an integer while1.0
means a real number. In Mathematica a 1 is a perfect one with infinite precision, while1.0
has only machine precision.k(1-t)
just meansk*(1-t)
. Parenthesis are used like in normal math too.