Question

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Answer 1

Bài 1.
1) 176 + 228 + 272 + 324
= (176 + 324) + (228 + 272)
= 500 + 500
= 1000
2) 526 - 131 - 326 + 321
= 526 + (-131) + (-326) + 321
= [526 + (-326)] + [321 + (-131)]
= 200 + 190
= 390
3) 545.65 + 15.545 - 80.445
= 545.(65 + 15) - 80.445
= 545.80 - 80.445
= 80.(545-445)
= 80.100
= 8000
4) 43.78 - 43.48 + 30.80 - 30.23
= 43. (78 - 48) + 30. (80 - 23)
= 43. 30 + 30. 57
= 30. (43 + 57)
= 30.100
= 3000
5) 2³.17 - 2³.14
= 2³. (17 - 14)
= 8.3
= 24
6) 2020 - [45 - (6 - 1)²] + 1992⁰
= 2020 - [45 - (5)²] + 1
= 2020 - (45 - 25) + 1
= 2020 - 20 + 1
= 2000 + 1
= 2001
 

Answer 2

Bài 3: 

1: \(\Leftrightarrow x-18=13\)

hay x=31

3: \(\Leftrightarrow x-5=15\)

hay x=20