Add, key, multiply, divide, bracket and other symbols in the following formula to make the number equal to 1. (1) 1 2 3 4 = 1 (2) 1 2 3 4 5 6 = 1

1 ×2 +3 -4 =1
1 +2+ 3- 4+ 5- 6=1

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1. How to add the bracket 1.7 × 0.9 + 1.2 △ 0.3-0.2 = 48.8 to make the formula hold! 1.7×0.9+1.2÷0.3-0.2=48.8 2.7×0.9+1.2÷0.3-0.2=18.3 3.7×0.9+1.2÷0.3-0.2=75 4.7 × 0.9 + 1.2 △ 0.3-0.2 = 47.6, there are four,
2. In the formula 6 × 4 + 18 ÷ 6 + 8, the minimum result is______ ．
3. According to the requirements, fill 1,2,2 / 1 in the brackets respectively, 5 / 8 divided by (), 5 / 8 divided by (), 5 / 8 divided by ()
4. With the four numbers of 1, 5, 6 and 7, through four operations and parentheses, what is the formula of 21?
5. Sin & # 178; a + cos & # 178; a = 1. What other formulas like this?
6. If a + B = m, ab = n, find the value of a & # 178; + B & # 178
7. Given (a + b) &# 178; = m, (a-b) &# 178; = n, find the value of: (1) (A & # 178; + B & # 178;) / AB; (2) ab It's represented by m, n
8. If we know (a + b) &# 178; = m, (a-b) &# 178; = n, then ab=_____
9. If a & # 178; - B & # 178; - 4 - () = A & # 178; + B & # 178; + AB, then the formula in () is? 1.8-8x/1.2-1.3-3x/2=5x-0.4/0.3
10. Please use the square difference formula: (a + b) (a-b) = A & # 178; - B & # 178;, calculate: 100 & # 178; - 99 & # 178; + 98 & # 178; - 97 & # 178; +... + 2 & # 178; - 1 & # 178;
11. Fill in the circle and box with the seven numbers 0, 1, 2, 3, 4, 5 and 6. Each number appears just once, forming an integer formula with only two digits and two digits
12. Add appropriate symbols and brackets to the following formula to make the equation hold. 1234 = 112345 = 1123456 = 11234567 = 1
13. Put the nine natural numbers 1-9 in the brackets below to make the formula hold. () × () = () × () = 5568“
14. Add some brackets to the following formula, so that the result of the formula is an integer and as small as possible. How to add brackets? 10 ﹣ 9 ﹣ 8 ﹣ 7 ﹣ 6 ﹣ 5 ﹣ 4 ﹣ 3
15. We can only use two plus signs and two minus signs to work out the following formula: 1 2 3 4 5 6 7 8 9 = 100
16. It is only allowed to write two minus signs, one plus sign and one bracket, without changing the numerical order. Connect the nine numbers 1.2.3.4.5.6.7.8.9, and the result is the formula of 100
17. (9 out of 16 + 9 out of 32-3 out of 8) * 4 out of 3 is calculated by simple algorithm, 11 out of 15 is divided by 7 + 1 out of 7 * 4 out of 15 is calculated by simple algorithm
18. Simple calculation of 5.16 + 3.8 × 1.2
19. Calculation: (5 + 1) (52 + 1) (54 + 1) (58 + 1) (516 + 1) + 14=______ ．
20. Calculation: 8 (3 ^ 2 + 1) (3 ^ 4 + 1) (3 ^ 8 + 1) (3 ^ 16 + 1) + 1 =? What method?