如題,解答一以下數題英文數學,答案合理或正確者將獲20點
1)Susan wants to buy a doll.She has no money now,so she starts to save $50 each week.If she saves $70 each week,she can save enough money 2 weeks earlier.How much is the doll?
2)(-5)+(-72) ÷(+9) = ?
3)(+45) ÷(-13)x(+26) = ?
4)Consider the expression (-1)x(-1)x(-1)x ...... x(-1).What is the value if the number of -1’s odd?What if the number of -1’s is even?Explain your answer briefly.
5)Write down 3 sets of values of a and b such that a is negative,b is positive and a+b is negative.For example,a = -5,b=3.
6)2 x (-5g) – 3 x (+4g) = ?
7)May has 15 plastic balls and 22 sticks.She use some plastic balls and sticks to make a hexagonal prism, are the remaining materials enough to make a triangular prism? Explain your answer briefly.
8)Given that ABCD is a rectangle.If the coordinates of A,B and C are (1,1),(1,6) and (3,6) respectively,find the coordinates of D.
9)Given that the distance between A(-5,-2) and B(x,-2) is 6 units.Are the coordinates of B unique? Briefly explain your answer.
小六升中一數學暑期作業英數問題幾則
2012-08-30 7:49 pm
回答 (2)
2012-08-30 8:57 pm
✔ 最佳答案
1)Let x be the number of weeks she needs if she saves $50 each weak.
50x=70(x-2)
50x=70x-140
-20x=-140
x=7
∴The cost of the doll=50x7=$350
2)
(-5)+(-72)÷(+9)
=(-5)+(-8)
=-5-8
=13
3)(+45)÷(-13)x(+26)
=45x26÷(-13)
=45x(-2)
=-90
4)
Let n be a positive integer.
When the number of -1's is even,
(-1)x(-1)x(-1)x ...... x(-1)
=(-1)^2n
=1^n
=1
When the number of -1's is odd,
(-1)x(-1)x(-1)x ...... x(-1)
=(-1)^(2n+1)
=1x(-1)
=-1
5)
a=-6, b=4
a=-7, b=5
a=-8, b=6
6)2x(-5g)–3x(+4g)
=-10g-12g
=-22g
7)
A hexagonal prism needs 6x2=12 plastic balls and 6x3=18 sticks.
∴The remaining materials are 3 plastic balls and 4 sticks.
However, a triangular prism needs 3x2=6 plastic balls and 3x3=9 sticks.
∴The remaining materials are not enough to make a triangular prism.
8)
X(1, 6) X(3, 6)
X(1, 1) X(D)
From the above, the coordinates of D are (3, 1).
9)
x-(-5)=6
x+5=6
x=1
I don't understand 'are the coordinates of B unique' mean. Please clarify it.
參考: me
2012-08-30 9:32 pm
1.
let x be original amount of week
y be the price of doll
50x=y ----(1)
70(x-2)=y ----(2)
sub (1) into (2),
70(x-2)=50x
70x-140=50x
20x=140
x=70
Therefore the doll is $70.
2. -13
3. -90
4. if odd, result= -1 if even, result= +1
5.a=-2 b=1
a=-10 b=3
a=-8 b=2
6. -22xg
7. hexagonal prism used up 12 balls and 18 sticks
triangular prism need 6 balls and 9 sticks
therefore its not enough to make a triangular prism
8. (3,1)
9. it's not unique, there are 2 answers
2012-08-30 13:35:21 補充：
sorry for Q1, x=7, y=50x7=350
doll= $350
let x be original amount of week
y be the price of doll
50x=y ----(1)
70(x-2)=y ----(2)
sub (1) into (2),
70(x-2)=50x
70x-140=50x
20x=140
x=70
Therefore the doll is $70.
2. -13
3. -90
4. if odd, result= -1 if even, result= +1
5.a=-2 b=1
a=-10 b=3
a=-8 b=2
6. -22xg
7. hexagonal prism used up 12 balls and 18 sticks
triangular prism need 6 balls and 9 sticks
therefore its not enough to make a triangular prism
8. (3,1)
9. it's not unique, there are 2 answers
2012-08-30 13:35:21 補充：
sorry for Q1, x=7, y=50x7=350
doll= $350
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