Deductive lambda calculus is a way of writing down mathematical equations. It is an important tool used by computer scientists and mathematicians to figure out the answers to hard problems.
A mathematical equation typically looks like "a + b = c". In deductive lambda calculus, instead of writing out an equation, you write out a set of instructions that tells you how to get the answer.
For example, you might have an equation that looks like "a + 3 = c". With deductive lambda calculus, you would write out the instructions that tell you how to get the answer. It would look like this:
1. Start with the number "a".
2. Add 3 to it.
3. That gives you the answer "c".
So by following the instructions, anyone can figure out the answer without having to do the math themselves.