Decomposition factor: (1) 2A (x-a) + B (A-X) - 3C (x-a) (2) (a ^ 2 + 1) ^ 2-4a ^ 2 (3) x ^ 2-2xy + y ^ 2 + X-Y

Decomposition factor: (1) 2A (x-a) + B (A-X) - 3C (x-a) (2) (a ^ 2 + 1) ^ 2-4a ^ 2 (3) x ^ 2-2xy + y ^ 2 + X-Y

The highway between the two towns is 75 kilometers long. Xiao Wang drives a car for 30 kilometers, sharing 2 liters of gasoline. According to this calculation, how many liters of gasoline does the car need to complete the whole journey?

2 △ 30 × (75-30), = 115 × 45, = 3 (liter). A: this car needs 3 liters of gasoline to complete the whole journey

If α is between 0 and 2 π, find the value range of α for sin α < cos α

For y = SiNx and y = cosx images, the following conditions are obtained: (0, π / 4) ∪ (5 π / 4,2 π)

There used to be a batch of 10 tons of cement on the construction site. Four ninth of this batch of cement was used for the first time and one third for the second time
How many parts of this batch of cement are left?

Consider this batch of cement as a whole
1-4/9-1/3
=5/9-1/3
=2/9

It is proved that when n is a natural number, the number of 2 (2n + 1) form cannot be expressed
1. Prove that when n is a natural number, the number in the form of 2 (2n + 1) cannot be expressed as the square difference of two integers
2. If a is a natural number, then a ^ 4 - 3A ^ 2 + 9 is prime or composite? Give your proof

1. Suppose that 2 (2n + 1) can be the difference between X ^ 2 and Y ^ 2
Then there is x ^ 2-y ^ 2 = 2 (2n + 1)
(x+y)(x-y)=2(2n+1)
Because X and y are natural numbers
So one of X + y and X-Y must be odd and the other even
If x + y is even, then X-Y must be even
If x + y is odd, then X-Y must be odd
So there is no value of X and y
2. When a is a multiple of 3. A ^ 4-3a ^ 2 + 9 must be a multiple of 3
When a is not a multiple of 3, it's hard to say

A and B have 280 tons of yellow sand in total. After a delivers 1 / 7 of the sand to B, their weight ratio is 3:4?

280÷（3+4）×3
=280÷7×3
=40×3
=120 tons
120÷（1-1/7）
=120÷6/7
=140 tons
280-140 = 140 tons
A: the two piles of yellow sand weigh 140 tons and 140 tons respectively
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F (x) is an odd function defined on [- 1,1]. If a and B belong to [- 1,1] and a + B is not equal to 0, then (f (a) + F (b)) / (a + b) is greater than 0
It is proved that f (x) is an increasing function on [- 1,1]

∵（f（a）+f（b））/（a+b）>0
(f (a) + F (- b)) / (a-b) > 0
∵ f (x) is an odd function defined on [- 1,1]
∴f(-b)=-f(b)
∴（f（a）-f（b））/（a-b）>0
That is: if a > b, then f (a) > F (b) (a, B ∈ [- 1,1]))
F (x) is an increasing function on [- 1,1]

If 30 people are sent from team a to team B, the ratio between team a and team B will be 3:2. How many people are there in each team?

3 + 2 = 5, 7 + 3 = 10, 30 ^ (25-310), = 30 ^ 110, = 300 (people); the number of team a: 300 × 710 = 210 (people); the number of team B: 300-210 = 90 (people); answer: the original number of team a is 210, the original number of team B is 90

Let x, y ∈ R, compare the size of x square + y square + 1. And XY + X + y
Let x, y ∈ R, compare the size of x square + y square + 1. And XY + X + y

Because (X-Y) & # 178; + (x-1) & # 178; + (Y-1) & # 178; ≥ 0
therefore
x²-2xy+y²+x²-2x+1+y²-2y+1≥0
2x²+2y²+2≥2xy+2x+2y
So x & # 178; + Y & # 178; + 1 ≥ XY + X + y

How many days are there in February 2012? The 30th Olympic Games will be held in London. This month is in the () quarter of the year. How many days are there in this quarter

February 2012 has 29 days. The 30th Olympic Games will be held in London in July of this year {July 27, 2012, 20:12 (London time). The London Olympic Games will last 17 days and close on August 12, 2012. This month is in the third quarter of this year, with a total of 92 days in this quarter