How to calculate E in high school mathematics?

How to calculate E in high school mathematics?

Is the base of natural logarithm, is an infinite non cyclic decimal. E is used very much in science and technology, generally do not use the logarithm with the base of 10. After learning advanced mathematics, you will know that many results and it has a close relationship, with E as the base, many formulas are the simplest, with it is the most "natural", so it is called "natural

How does it work

n!= 1*2*3*4…… *（n-3）*（n-2）*（n-1）*n
for example
4!=1*2*3*4

It is known that the odd function y = f (x) is defined on [- 1,1] and is a decreasing function in the domain of definition. If f (a2-a-1) + F (4a-5) > 0, the value range of real number a is obtained

Because f (a2-a-1) + F (4a-5) > 0, so f (a2-a-1) > F (4a-5), because the function y = f (x) is odd, so the above formula becomes f (a2-a-1) > F (- 4A + 5), and because the function y = f (x) defined on [- 1, 1] is a decreasing function, so − 1 ≤ A2 − a − 1 ≤ 4A − 5 ≤ 1