(1 + X + 1 / x) to the 10th power, how can the constant term in the expansion be calculated: the answer is - C (10,0) + C (1,3) C (3,10)... How are two multiplications? How

(1 + X + 1 / x) to the 10th power, how can the constant term in the expansion be calculated: the answer is - C (10,0) + C (1,3) C (3,10)... How are two multiplications? How

Note that (1 + X + 1 / x) to the 10th power can be changed to the 10th power of [(x + x square + 1) / x]
The denominator is the tenth power of X, and the numerator is the tenth power of (x + x square + 1)
In other words, what this topic requires is that x in the molecule is left with a power of 10, so that the remaining constants can be eliminated. I think we should know how to do this topic by now. If we divide three numbers and add them together, we can regard them as two sums, one of them as a number, and then we can divide them together again. Another is experience. If we see more, we will know what it is