中一數學!!!!!!!!!!!!help!!!!!!20点!

張家寶

2010-08-23 11:17 pm

1.

find the value of the expression(+1)+(-2)+(+3)+(-4)+...+(+99)+(-100)without usinga calculator

2.

consider the equation x-2x+3x-4x+5x-6x...+99x-100x=200,Solve the equation and briefly explain how you can solve it.

3.

in the expression(ax+b)(cx*cx+dx+e),find two sets of values of a,b,c,d,e so that the coefficients of x*x*x and x terms after expansion are 4 and 10 respectively.

4.

draw 3 figures each having 2 axes of symmetry and 2-fold rotation symmetry.mark also the axes of symmetry and the centres of rotation on the figures

5.

initially the robot was at (0,0).after running program x for 99 times,the battery level can support the robot to complete 2 more steps.where did the robot stop?show the steps how you find the coordinates.
program start
step1 move 4 units to the right
step2 move 5 units upwards
step3 move 3 units to the left
step4 move 5 units downwards

6.

john paid $41 for 6 packs of biscuits and 2 bags of chips.it $11.5 is needede for 1 pack of biscuits and 1 bag of chips.what's the price of a pack of biscuits and the price of a bag of chips?

回答 (1)

Tommy

2010-08-24 1:51 am

✔ 最佳答案

1) group the number first
+1-2=-1
+3-4+-1
....
total 50group
ans: -50

2)by considering the first question
you can apply the ans in first question
-50x = 200
x = -4

3) (ax+b)(cx*cx+dx+e)
=ac^2x^3 + adx^2 +aex +bc^2x^2 + bdx +be
=(ac^2)x^3 + (ad +bc^2)x^2 + (ae+bd)x +be

as coefficient of x*x*x is (ac^2) = 4
and coefficient of x is ae+bd =10

for the factor of 4, it is 1,2,4
consider ac^2 =4
first set of a =4 and c =1 or second set
a = 1 and c =2

as first set of a =4 and c =1 , only a affecting the coefficient of x
you can say e = 1 and b = 2, d =3

for the second set a = 1 and c =2
e = 6 b=1 d = 4

in this question how to solve ac^2 is the main point.

4)As I can't draw the pictures here, I can only tell some brands logo to you that fullfill your requirement,

HSBC
CHINA BANK
UMBO

those brand logos can fullfill your requirment.

5)
first consider the net movement of 4step together
then count 2more steps.

net movement of those 4 steps is going to right 1unit.
after 99times, it stops at (99,0)
run two more steps,
step1 move 4 units to the right
step2 move 5 units upwards

the location is at (103,5)

6)

2packs of of biscuits and 2 bags of chips = 11.5X2 =$23

41 - 23 = 18
so, 4packs of biscuits sold at a price $18
1 pack of biscuits is sold at $4.5

as 2packs of of biscuits and 2 bags of chips =$23
2 packs of biscuits sold at a price $9
23-9=$14
so 1bag of chip is at a price $7

2010-08-23 17:56:51 補充：
In QUESTION 4 SHOULD BE UMBRO NOT UMBO

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