Select 10 from 1 / 2,1 / 3,1 / 4,1 / 5 -- 1 / 90,1 / 91 and add the sign to make the sum equal to - 1

Select 10 from 1 / 2,1 / 3,1 / 4,1 / 5 -- 1 / 90,1 / 91 and add the sign to make the sum equal to - 1

-1/2-1/4-1/5-1/20+1/3-1/5-1/15-1/30-1/45-1/90=-1
Front 4 = - 1
The last six are equal to zero

At 1 / 2, 1 / 3, 1 / 4, 1 / 5 Select 10 numbers from 1 / 90 and 1 / 91, add the sign to make them equal to - 1

- 1 = - 1 / 5-1 / 6-1 / 8-1 / 9-1 / 10-1 / 12-1 / 15-1 / 18-1 / 20-1 / 24 1-1 / 2 + 1 / 2-1 / 3 + 1 / 3-1 / 4 + 1 / 4-1 / 5 + 1 / 5-1 / 6 + 1 / 6-1 / 7 + 1 / 7-1 / 8 + 1 / 8-1 / 9 + 1 / 9-1 / 10 = 1-1 / 10, so: 1 / 2 + 1 / 6 + 1 / 12 + 1 / 20 + 1 / 30 + 1 / 42 + 1 / 56 + 1 / 72 + 1 / 90 + 1 / 10 = 1

What symbol in the middle of 9 7 5 4 is equal to 24?
Do you want to know the correct answer? I tell you, when I submitted the answer just now, I couldn't submit it because you determined the wrong answer?
What symbol in 9 7 5 4 is equal to 24? The order of 9 7 5 4 can't be changed. [Note: it's all wrong to change the order]; this question is raised by "cx634952766", so it's put forward again for lovers to think about ﹣ don't attack!

√9=3 3*7=21 21+5=26 √4=2 26-2=24