36 × (3 / 4-9 / 1 + 1 / 6) 3 × (2 / 15 + 1 / 12) - 2 / 5 4 / 9 (4 / 5 - (1 / 5 + 1 / 3)) (1 / 2 (3 / 4-3 / 5)) / 70%

36 × (3 / 4-9 / 1 + 1 / 6) 3 × (2 / 15 + 1 / 12) - 2 / 5 4 / 9 (4 / 5 - (1 / 5 + 1 / 3)) (1 / 2 (3 / 4-3 / 5)) / 70%

36 × (3 / 4-9 / 1 + 1 / 6) = 36 × 4 / 3-36 × 9 / 1 + 36 × 6 / 1 = 27-4 + 6 = 293 × (2 / 15 + 1 / 12) - 5 / 2 = 3 × 15 / 2 + 3 × 12 / 1-5 / 2 = 5 / 2 + 4 / 1-5 / 2 = 4 / 19 / 4 (4 / 5 - (1 / 5 + 1 / 3)) = 9

The average number of M is a, the average number of n is B, and the average number of P is C. what is the average number of (M + N + P)?

(M*A+N*B+P*C)/(M+N+P)

Junior high school mathematics problems
Now there is one line segment of length 1,2,3,4,5,6,7,8,9, from which several line segments are selected to form a "line segment group". This group of line segments can just be put together into a square. What is the number of such "line segment group"?

Let the side length be n,
Then 1 + 2 +... + n > = 4N
That is n (1 + n) / 2 > = 4N
The solution is n > = 7
1+2+...+9=9*10/2=45
Then the side length should be less than 45 / 4, that is n

The radius of the round table is 60cm, and the distance between each person and the round table is 10cm. Now there are two more guests. Each person moves back the same distance, and then adjusts his position to the left and right, so that all eight people sit down, And the distance between the 8 people is equal to the distance between the original 6 people (that is, the length of the arc between the two people on the circle). Suppose that the distance of each person moving backward is X. according to the meaning of the question, the equation ()
Option 1.2 π (60 + 10) / 6 = 2 π (60 + 10 + x) / 8
Option 2.2 π (60 + x) / 8 = 2 π times 60 / 6
Option 3.2 π (60 + 10) times 6 = 2 π (60 + x) times 8
Option 4.2 π (60-x) times 8 = 2 π (60 + x) times 6
Problem 2: the speed of a ship downstream between the two banks is 21km / h, and the speed of a ship upstream is 18km / h. If the speed of the ship in still water is constant, the water flow speed is (write down the calculation process)

The first question is option 1
In the second question, let the water velocity (water velocity) be x and the still water velocity (ship velocity) be y, then
1 formula y + x = 21
Formula 2 Y-X = 18
Formula 1 minus formula 2 2x = 3
x=1.5
So the water velocity is 1.5km/h

This is the solution of a problem
T=10y+8.5(100-x)
=10y-8.5x+850
=x((10y/x)-8.5)+850
Because t has nothing to do with X
So 10Y / x-8.5 = 0
Why is the first X and 850 in X ((10Y / x) - 8.5) + 850 removed, while the X in brackets is not removed
What is the meaning that has nothing to do with x

10y-8.5x+850
How to get it
x((10y/x)-8.5)+850
Please look back
10y/x*x-8.5*x+850
=10y-8.5x+850

Hyperbola y = K / X and straight line y = x intersect at two points a and B (point a is in the first quadrant). If OA = 2 radical 2, translate straight line AB upward by M units, and the resulting straight line intersects with X and y at two points c and D respectively
(1) Finding the coordinates of two points a and B and the hyperbolic analytic formula
(2) When m = 2, judge the shape of quadrilateral ABCD and explain the reason
Point P is on the straight line CD. The quadrilateral with a, B, C and P as the vertex is a parallelogram. Find the coordinates of point P

1. Let a (a, a), then Ao = square of root 2A = root 2 × a = 2, root 2, so a = 2, so a (2,2)
And point B and point a are symmetric about the origin, so B (- 2, - 2), so k = 2 × 2 = 4, the analytic formula of hyperbola is y = 4 △ X
2. It is easy to know that point C is (0,2), the analytic formula of the moving line is y = x + 2, then the intersection point with the Y axis is (- 2,0), so BD = 2, connecting AC, because Ao = 2, radical 2, CO = 2, ∠ AOC = 45 °, so AC = 2, and ab ‖ CD, so ABCD is isosceles trapezoid
(1) For parallelogram ABPC, then CP = AB = 4, radical 2, so p is (4,6)
(2) The parallelogram ABCP, similarly P is (- 4, - 2)

If: | a + B + 1 | and (a-b + 1) 2 (this 2 is the second power of other gate above A-B + 1) are opposite numbers, then what is the size relationship between a and B?
Simplify | 3x-2 | + | 2x + 3 |? | X-1 | - 3 | + | 3x + 1|

1. Because: | a + B + 1 | and (a-b + 1) 2 are opposite numbers
So a + B + 1 ≥ 0
So a ≥ - 1-B
The solution is: B = 0, a = - 1
A is less than B
2. One: if x is greater than 2 / 3, then 5x + 1
2： If x is less than - 3 / 3, then - 5x-1
3： If it is between the two, then 5-x

If the parabola y = - x2 + 2 (m-1) x + m + 1 intersects with y axis at two points a and B of X axis, and point a intersects on the positive half axis of X axis, point B is on the negative half axis of X axis, the length of OA is a, and the length of ob is B
(1) Find the value range of M
(2) If a: B is 3:1, find the value of M and write the analytical formula of the parabola
(3) Let the parabola in (2) intersect with the y-axis at point C, and the vertex of the parabola is m. question: is there a point P on the parabola, so that the area of △ PAB is equal to 8 times of the area of △ BCM? If so, calculate the coordinates of point P. if not, please explain the reason
I'm sorry, it's the intersection of the parabola (x 2 + 1) and the parabola (x 2 + 1)

(1) A is on the positive half axis of X, B is on the negative half axis
So X1 * x2 = - (M + 1) - 1
（2）|a|=3|b|
Let the two roots of y = 0 be x1, x2
x1+x2=3a-a=2a=2(m-1)
a=m-1
x1*x2=3a*(-a)=-3a^2=-(m+1)
-3(m-1)^2=-(m+1)
3m^2-7m+2=0
m=2,m=1/3
M = 1 / 3, y = - x ^ 2-4x / 3 + 4 / 3, but when y = 0, x = - 2 and 2 / 3 respectively
So m = 2, y = - x ^ 2 + 2x + 3
(3) Third, ask yourself to discuss it separately according to the second question. When calculating the area of the triangle BCM, take the side on the y-axis as the bottom to calculate the sum of the areas of the two triangles. You can calculate it yourself
There are three points P, whose coordinates are P1 (1,4), P2 (1 + 2, - 4), P3 (1-2, - 4)

Let n be a positive integer such that
1 1 1 19
—— + ------ + ----- ＞ -------
1+N 3+N 6+N 36
Find the maximum of n
The answer is that the maximum value of n is 2

This problem is simple, because n is in the denominator, so with the increase of N, the value on the left side of the inequality will decrease, that is to say, there will always be an n that makes the inequality hold, and N + 1 will make the inequality not hold. What we need to do is to find out this n. if it is the solution, you can write it like this, because n is in the denominator, so if n increases, then the inequality

Junior high school mathematics one variable quadratic equation application problem, growth rate problem,
In order to meet the Guangzhou Asian Games, Yucai Middle School planted 1979 trees in four years from 2007 to 2010. It is known that the school planted 342 trees in 2007 and 500 trees in 2008. If the growth rate of trees planted in 2009 and 2010 is the same, what is the number of trees planted in 2010?

Let the growth rate be X500 (1 + x) + 500 (1 + x) (1 + x) + 500 + 342 = 1997