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Zhejiang Education Press seventh grade mathematics homework review questions
The most important thing is the last question. I hope it can be before 9 o'clock. Please. If you want to know the data in the blank, you can set the number of students in Grade 7 as X and the number of students in Grade 8 as y
We can use geometry to explain some algebraic identities,
Figure a can be used to explain (2a) 2 = 4A 2
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Let's not talk about it next. The reason for the homework,
Water is composed of hydrogen and oxygen. The mass ratio of hydrogen and oxygen is 1:8.100g. Water contains more hydrogen and oxygen
The relative molecular mass of water is 18
The mass fraction of hydrogen = 2 / 18 = 1 / 9
Mass fraction of oxygen = 16 / 18 = 8 / 9
So the mass of hydrogen in 100g water = 100 * 1 / 9 = 11.1g
Mass containing oxygen = 100 * 8 / 9 = 88.9g
If a = 2, then a & # 178; + B & # 178; a & # 178; - AB + B & # 178=
a/b＝2
a＝2b
∴ ﹙a²－ab＋b²﹚/﹙a²＋b²﹚
＝﹙4b²－2b²＋b²﹚/﹙4b²＋b²﹚
＝3b²/5b²
＝3/5
How much is five eighths minus five eighths?
13 times 5 / 6 minus 5 / 6 = 13 * 5 / 6-5 / 6 = 5 / 6 * (13-1) = 5 / 6 * 12 = 10 3 / 8 minus 7 / 15 times 3 / 8 = 3 / 8-7 / 15 * 3 / 8 = 3 / 8 * (1-7 / 15) = 3 / 8
(13 out of 18 * 5.16 + 516% * 3 out of 18) △ 5 and 4 out of 25 is simple, the number seems to be 8 out of 9
(13 of 18 * 5.16 + 516% * 3 of 18) △ 5 and 4 of 25
=(13 of 18 * 5.16 + 5.16 * 3 of 18) △ 5.16
=5.16 × (13 / 18 + 3 / 18) △ 5.16
=16 out of 18
=8 out of 9
246*17-123*33
13936870124 ,
246×17－123×33
＝123×2×17－123×33
＝123×（34－33）
＝123
If a & # 178; + AB = 20, B & # 178; - AB = 13, then a & # 178; + B & # 178; =? A & # 178; + 2ab-b & # 178; =?
a²+ab=20,①
b²-ab=13 ②
① + 2 is a & # 178; + B & # 178; = 33
① (2) a-178; + 2ab-b-178; = 7
Fill in the blanks 1. (- 7) + () = 21 2.31 + () = - 85 3. () - (- 21) = 37 4. () - 56 = - 40 calculate 1. (- 72) - (- 37) - (- 22) - 17
2. (- 16) -(- 12) - 24 - (- 18) 3, 23 - (- 76) - 36 - (- 105) 4
28
-116
sixteen
sixteen
calculation:
1.-30
2.-10
three point one six eight
4.-164
Up nine meters
[x + 1] [x + 2] plus quarter factorization
(x+1)(x+2)+1/4
=x²+3x+2+1/4
=x²+3x+9/4
=x²+2*3x/2+(3/2)²
=(x+3/2)²
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