Winter vacation homework has a new definition in recent years, and a few schools have carried out high-quality practical activities, which have turned winter vacation homework into activities and enriched students' after-school life. The following is my answer to winter vacation homework's seventh grade mathematics. Welcome to refer to it!
Winter vacation homework's answer to seventh grade mathematics-1. Enter the wonderful world of mathematics.
1.9(n- 1)+n = 10n-9 2.630 3。 =36% 4. 133,23 2000=2453 ?
5.？ 2520,? a=2520n+ 1 6。 A seven. C 8。 B 9。 C 10。 C
1 1.6, two digits 95 must be the divisor of 2003-8 = 1995, and 1995=3? 5? 7? 19
12. 13.
14. Observing the graphic data, we can get the rule that an N prism has (n+2) faces, 2n vertices, 3n? Stripes.
15.D 16。 A 17。 C S will not decrease with the increase of t, and the distance will not change within a few minutes of the delay in repairing the car. Continue to drive at a constant speed after repairing the car, and the distance should be increased.
18.C 9+3？ 4+2? 4+ 1? 4=33. 19.
20.( 1)(80-59)? 59? 100%? 36% (2) 13? 80? 100%? 16% ?
(3)? 1995? What is the growth rate from ~ 1996 (68-59)? 59? 100%? 15%,
The growth rate of other years can be obtained by the same method, and the highest growth rate is 1995 ~ 1996.
2 1.( 1) The list of promotion methods of Mall B is as follows:
Buy more than 24 sets11~ 8 sets of 9 ~ 16 sets 17 ~ 24 sets.
Unit price: 720 yuan, 680 yuan, 640 yuan and 600 yuan.
(2) Comparing the promotion methods of the two shopping malls, we can see that:
Buy 1 ~ 5, 6 ~ 8, 9 ~ 10,1~15.
Select shopping malls b, b, b, b.
Buy 16 sets, 17 ~ 19 sets, 20 ~ 24 sets, more than 24 sets.
Select shopping malls a, b, a and b.
Because it costs 600 yuan to buy a 2 1 vcd in a shopping mall? 2 1= 12600 yuan, buy 20 yuan from Mall B? Taiwan Province VCD? * * * Need 640? 20= 12800 yuan,12800 > 12600,
So when you buy 20 VCDs, you should go to the mall to buy them.
Therefore, Unit A should go to Shopping Center B, Unit B should go to Shopping Center A, and Unit C should go to Shopping Center A. 。
22.( 1) Arrange divisible rectangles with integer sides from small to large according to conditions, including
1? 1, 1? 2, 1? 3, 1? 4,2? 2, 1? 5,2? 3,2? 4,3? 3,2? 5,3? 4,3? 5.
If it can be divided into five eligible papers, because the sum of their areas should be 15, the eligible papers are
1? 1, 1? 2, 1? 3, 1? 4, 1? 5 (Figure ①) or 1? 1, 1? 2, 1? 3,2? 2, 1? 5 (Figure ②)
2. From arithmetic to algebraic answers
1.n2+n = n (n+1) 2.109 3.4.150 minutes 5.c6.d7.b8.b
9.( 1)S = N2(2)① 100② 132-52 = 144(3)n = 15
10.( 1)a =。
1 1.S=4n-4 12。 b2 13.595 14。 ( 1) 18; (2)4n+2
15.a Let the natural number start from a+ 1, and the sum of these 100 consecutive natural numbers is
(a+ 1)+(a+2)++(a+ 100)= 100 a+5050。
The first column number of 16.c can be expressed as 2m+ 1, and the second column number can be expressed as 5n+ 1.
From 2m+ 1=5n+ 1, n= m, m = 0,5, 10? 1000
18.d Hint: Each student moves bricks every hour, and C students move bricks every hour at this speed.
19. Hint: a 1= 1, a2=, a3=, an=, the original formula =.
20. If each calculator is X yuan, and each book in the math contest handout is Y yuan, then 100(x+3y)=80(x+5y), which means x=5y, then you can buy a calculator = 160 (sets) and a book =800 (volumes).
(2) If it can be divided into six pieces of paper that meet the requirements, the sum of their areas should still be 15. But the sum of the areas of the above six rectangles is 1? 1+ 1? 2+ 1? 3+ 1? 4+2? 2+ 1? 5= 19 > 15. So it is divided into 6 parts? It is impossible to get a piece of paper that meets the requirements.
3. The cornerstone of creation-observation, induction and guessing the answer
1.( 1) 6, (2) 2003.2.A+B = C+D- 14 or a+c=b+d-2 or A+D = B+C3. 13, 3n+. C
5.b Tip: The number that appears in these two character strings at the same time is the integer from 1 to 1999 divided by 6, which has 334 * *.
6.C
7. Tip: Observe the written numbers and find that there is an even number in every three consecutive numbers, which is in the previous 100 item. 100 is odd, and the first 99 items have =33 even numbers.
8. Tip: The arrangement characteristics of this natural number table can be obtained through observation:
(1) Every number in the first column is a complete square number, and it is exactly equal to the square of the number of rows where it is located, that is, the number of the nth row 1 is N2;
(2) the first line n? The number is (n-1) 2+1;
③ Line n, decreasing from the first digit to the nth digit1;
④ The number of the nth column counting from the first to the nth increases by 1.
It can be found that the number of line 1 0 starting from (1) and the number of column 13 starting from the left should be the number of column 10, that is
[( 13- 1)2+ 1]+9= 154.
(2) The number 127 satisfies the relation 127 =112+6 = [(12-1) 2+1]+5, that is. The position of the line.
9.( 1)(2n+ 1)(2n+3)= 4(n+ 1)2- 1；
(2),-The number of rows is 1, 2, 3,? From 1 line to 198 line, from 1 line to 1997 line, it is easy to find out how many problems there are.
10.7N+6，285 1 1。 Lin 12. S=7？ 4(n- 1)-5n=23n-8(n？ 3) 13.B 14。 C
15.( 1) Hint: Yes, the original formula =? 5;
(2) The original formula = there are n- 1 odd numbers in the result.
16.( 1) omitted; (2) number of vertices+number of faces-number of edges = 2; (3) Drawing as required to verify the conclusion of (2).
17.( 1) Generally speaking, we have (a+ 1)+() = = (a+ 1)?
(2) Similar problems such as:
(1) What are two numbers whose difference is equal to their quotient? (2) What kind of three numbers, their sum is equal to their product?
4. Reciprocal and absolute value answers
1.( 1)A； (2)C； (3)D 2。 ( 1)0; (2) 144; (3)3 or -9
3.a=0，b=。 Original formula =- 4.0,? 1,? 2,? ,? 1003. Its total is 0.
5.a= 1，b=2。 Original formula =.
6.a-c 7.m= -x3，n= +x。
∫m =(+x)(+x2- 1)= n[(+x)2-3]= n(N2-3)= n3-3n。
8.p=3，q=- 1。 Original formula =669? 3-(- 1)2=2006.
5. Birds of a feather flock together-the answer to similar items
1. 1 2.( 1)-3, 1 (2)8.3.4000000 4.-4 5.C 6。 C 7。 An eight. A
9.D=？ 3x2-7y+4y2，F=9x2- 1 1xy+2y2
10. 12 hint: according to the meaning of the question, B = m- 1 = n, C = 2n- 1 = m, 0.625a = 0.25+(-0. 125).
1 1. Right 12. - 13.22
Tip: a>b, the original formula =a,?
Therefore, it is known that the result of substituting two numbers in each group into algebraic expression is the larger of the two numbers.
On the whole, as long as 5 1, 52, 53, 100 is 50? Substituting numbers into each group in turn can get the maximum sum of 50 values.
15.d16.d17.b18.b Hint: 2+3+? +9+ 10=54，8+9+ 10=27。
6. The solution of one-dimensional linear equations
1.- 105.
2. Let the original input number be x, then-1=-0.75, and the solution is x=0.2.
3.- ; 90 4.、- 5.？ d？ 6. A seven. An eight. B
9.( 1) when a? B, the equation has a unique solution x =；; When a=b, the equation has no solution;
(2) when a? At 4 o'clock, the equation has a unique solution x =；;
When a=4 and b=-8, the equation has countless solutions;
When a=4 and b? At -8, the equation has no solution;
(3) when k? 0 and k? At 3 o'clock, x =；;
When k=0 and k? 3. The equation has no solution;
When k=3, the equation has countless solutions.
Winter vacation homework answer 2 1 in seventh grade mathematics. Multiple choice questions
1A 2D 3A 4C
fill (up) a vacancy
( 1)T=20-6h 20，6 T h h
(2)Q = 6x 105-pt 6x 105 p Q t 0？ t？ 6x 105/ piece
(3)S= 1.5b (4) 0？ x？ 7 0? y？ 5 5 0
solve problems
( 1)y= Q/a-x？ Q/A (0? x？ answer
(2)y=80-2x
20(3) ①-2? x？ three
② When x=3, the minimum value of y is 1/2.
3 When? -2. x？ 0, y increases with the increase of x, when 0? x？ 3, y decreases with the increase of x.
(4)①`v=800-50t
②0? t？ 16
③ When t=8, v=800-50x8=400.
④ When v= 100, 100=800-50t.
T= 14
Page five? Page 7
Multiple choice
1B 2C 3C 4B 6A 7B 8D
fill up a vacancy
( 1) 1(2)y = 2x+ 1- 1(3)m & lt； 2n & lt； 3 (4)y=-3x+3
(5)y = x+3(6)y = 64x+48(7)S = 2n+ 1(8)y = 1/5 x-6 30
answer the question
(1) let y = kx+b.
-4k+b= 15
6k+b= -5
k= -2 b=7
y= -2x+7
(2) Omission
(3)① indicates the relationship between y and x, and x is the independent variable.
② Leaving home1010km1330km.
③ 30km away from home12-13.
④13km
⑤2: 00 - 13: 00
615km/h
Page 9? Page 1 1
1. Multiple choice problem
( 1)A (2)C (3)C
fill (up) a vacancy
( 1)y =-2x(2)m & lt； 2(3)y = 5x+3(4)y2 & gt； y 1(5)y =-2x+ 100 25(6)9
solve problems
( 1) ① Q=200+20t② (0？ t？ 30)
(2) ①y=80 (0？ x？ 50)
y= 1.9x- 15 (50？ x？ 100)
②y= 1.6x
③ Option 1
(3)① y=25/72x on the same straight line
② When x=72, y=25.
When x= 144, y=50.
When x=2 16, y=75.
y=25/72 x (0？ x？ 345.6)
③ When x= 158.4, y=25/72x 158.4=55.
(4) ①y A =2x+ 180
Y B =2.5x+ 140
② when x= 100, Y A =200+ 180=380.
Y B = 140+250=390
380〈390
Renting armored vehicles is more flexible.
Page 13? Page 15
1. Multiple choice problem
( 1)D (2)C (3)C
fill (up) a vacancy
( 1)x=2
y=3
(2)x = 2x & gt； 2
(3)-3 -2 x= -5/8 y= - 1/8
(4) 1/2 0 x=2
y=3
(5)y=5/4 x
solve problems
3.( 1) Omit
(2)① According to the meaning of the question
-k+b= -5
2k+b= 1
solve
k=2 b= -3
y=2x+3
When will you? 0 o'clock
2x-3？ 0，x？ 3/2
② when x
2x-3
That is y < 1
(3) ①y membership card =0.35+ 15
Y book card = 0.5x
② If Y membership card < Y book rental card
Then 0.35x+ 15
x & gt 100
If the book is rented for more than 100 days, the membership card is more cost-effective than the book rental card.
(4) let A(m, n)
1/2x4xm=6
m=3
n=2
One (-3, -2)
y=2/3x，y= -2/3x -4
(5)①y A = 0.8x 1.5x+900 = 1.2x+900(x？ 500)
y B = 1.5x+900 x 0.6 = 1.5x+540(x？ 500)
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