A rectangular piece of paper is 25 cm long and 20 cm wide. Cut the largest circle on this piece of paper. After cutting the circle, what is the remaining area?

2, = 3.14 × 100, = 314 (square centimeter); 25 × 20-314, = 500-314, = 186 (square centimeter); a: the remaining area is 186 square centimeter

A and B each bought the same number of envelopes and stationery. For each letter sent by a, a used only one piece of stationery, while B used three pieces of stationery. As a result, a used all the envelopes, but the remaining 50 pieces of stationery, while B used all the stationery, but the remaining 50 envelopes. Then the number of stationery and the number of envelopes bought by a and B were
A150,100 B125,75 C120,70 D100,150

Let X be the number of letters and y be the number of envelopes
x-y=50
y-(x/3)=50
Solution
x=150,
y=100
A: Party A and Party B bought 150 letters and 100 envelopes

Let three mutually unequal rational numbers be expressed in the form of 1, a + B, a, and also in the form of 0, B △ a, B, and find the value of a (DE) 2007 (power) + B (DE) 2008 (power)
It's not that I haven't thought about this question, but I still can't understand some aspects. Maybe I don't know enough about it. And, let's bow deeply

Because in B △ a, a is the denominator
So a is not equal to 0
Then: a + B = 0
So a and B are opposite to each other
Then: B / a cannot be positive
So B / A is not equal to 1
Then: B = 1
Because a and B are opposite numbers
So a = - 1
The value of a is - 1, and the value of B is 1
2007 power of a + 2008 power of B = - 1 + 1 = 0

If the vertex of the parabola y = - x ^ 2 + BX + C is in the third quadrant, then the root of the quadratic equation x ^ 2-bx-c = 0 is

If the opening of the parabola is downward and the vertex is in the third quadrant, then there is y

There are 78 tons of yellow sand in pile a and pile B. If 1 / 5 of pile a is transferred to pile B, pile a is 2 tons more than pile B, so it is necessary to calculate the quantity of yellow sand in pile a and pile B

Suppose: pile a has x tons, and pile B has 78-x tons
4/5x=78-x+1/5x+2
8/5x=80
x=50
Therefore, the original 50 tons of pile a, the original 78-50 = 28 tons of pile B

If m, n ∈ [- 1,1], M + n is not equal to 0, then f (m, n ∈ [- 1,1]) is an odd function over the domain_ )+f(n)/m+n>0
The monotonicity of FX on [- 1,1] is judged and proved

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

Given x + y = 8, xy = 12, find the value of x 2 + y 2

The original formula = (x + y) 2-2xy, when x + y = 8, xy = 12, the original formula = 82-2 × 12 = 40

At the 2012 London Olympic Games, Chinese athletes won () gold medals, ranking () in the gold medal list

38 pieces

Try to compare the size of x 2 + y 2 and XY + X + Y - 1

∵ x2 + Y2 - (XY + X + Y-1) = X2 - (y + 1) x + y2-y + 1 = (x − y + 12) 2 − 14 (y + 1) 2 + Y2 − y + 1 = (x − y + 12) 2 + 34 (Y − 1) 2 ≥ 0 (10 points) ∵ x2 + Y2 ≥ XY + X + Y-1

A rectangular piece of paper is 25 cm long and 20 cm wide. Cut the largest circle on this piece of paper. After cutting the circle, what is the remaining area?