Calculation: 2 + 2 ^ 2-2 ^ 3-2 ^ 4 -2^19-2^20+2^21=

Calculation: 2 + 2 ^ 2-2 ^ 3-2 ^ 4 -2^19-2^20+2^21=

The problem of summation of equal ratio sequence:
2+2^2-2^3-2^4…… -2^19-2^20+2^21
=2+2^2+2^21-(2^3+2^4+.+2^20)
=2+2^2+2^21-(2^21-2^3)
=2+2^2+2^3
=14
If you don't understand, ask me again, I'll be more detailed,

The product of a number and minus one and twenty-three is minus four and twenty-nine

Minus four and nineteen twenties △ minus one and thirteen twenties = 3

The product of a number and minus one and twenty-three is four and twenty-nine

x (-33/20)=99/20
x=99/20*(-20/33)
x=-3