Question

Helpppp confused

Answer 1

Not an expertise on infinite sums but the most straightforward explanation is that infinity isn't a number.

Let's see if there are anything we missed:

 ∞

 Σ  2^n=1+2+4+8+16+...

n=0

We multiply (2-1) on both sides:

       ∞

(2-1)  Σ  2^n=(2-1)1+2+4+8+16+...

      n=0

And we expand;

 ∞

 Σ  2^n=(2+4+8+16+32+...)-(1+2+4+8+16+...)

n=0

But now, imagine that the expression 1+2+4+8+16+... have the last term of 2^n, where n is infinity, then the expression of 2+4+8+16+32+... must have the last term of 2(2^n), then if we cancel out the term, we are still missing one more term to write:

 ∞

 Σ  2^n=-1+2(2^n)

n=0

If n is infinity, then 2^n must also be infinity. So technically, this goes back to infinity.

Although we set a finite term for both expressions, the further we list the terms, they will sooner or later approach infinity.

Yep, this shows how weird the infinity sign is.