Mathematics, formula 0.3+0.6+0.9+1.2+1.5+1.8+2.1+2.4= Note: it is expressed by algebraic expression containing n

Mathematics, formula 0.3+0.6+0.9+1.2+1.5+1.8+2.1+2.4= Note: it is expressed by algebraic expression containing n

0.3*n(n+1)/2
n=8
*It's a multiple sign

The concept arrangement of mathematics geometry in grade one of junior high school

Mathematics concept of grade one in junior high school
Real number:
Rational numbers and irrational numbers are called real numbers
Rational number:
Integers and fractions are called rational numbers
Irrational number:
Irrational number refers to the infinite non cyclic decimal
Natural number:
The number of objects 0, 1, 2, 3, 4 ～ (0 included) are called natural numbers
Number axis:
A straight line that specifies a dot, a positive direction, and a unit length is called a number axis
Opposite number:
Two numbers with different symbols are opposite to each other
reciprocal:
Two numbers whose product is 1 are reciprocal to each other
Absolute value:
The absolute value of a is the distance between a point on the number axis and a circle point. The absolute value of a positive number is itself, the absolute value of a negative number is its opposite, and the absolute value of 0 is 0
Mathematical theorem formula
The algorithm of rational number
(1) addition rule: add two numbers with the same sign, take the same sign, and add the absolute value; add two numbers with different signs, take the sign of the addend with the larger absolute value, and subtract the smaller absolute value from the larger absolute value, and add two numbers that are opposite to each other to get 0
Subtraction rule: subtracting a number is equal to adding the opposite number of the number
(3) multiplication rule: if two numbers are multiplied, the same sign will get positive, the different sign will get negative, and the absolute value will be multiplied; if any number is multiplied by 0, it will get 0
(4) division rule: divide a number by the reciprocal of the number; divide two numbers by the same sign to get positive, different sign to get negative, and divide the absolute value by each other; divide 0 by any number that is not equal to 0 to get 0
Bisector of an angle: a ray is drawn from a vertex of the angle, which can divide the angle into two parts equally. This ray is called the bisector of the angle
Mathematics Chapter 1 intersecting lines
1、 Adjacent complementary angle: in the four corners formed by the intersection of two straight lines, there is a common vertex and a common edge. This angle is called adjacent complementary angle. Adjacent complementary angle is a kind of angle with special positional and quantitative relationship, that is, adjacent complementary angle must be complementary angle, but complementary angle is not necessarily adjacent complementary angle
2、 Opposite vertex angle: it is formed by the intersection of two straight lines. The two sides of the two angles are opposite extension lines to each other, so opposite vertex angle can also be said to be "opposite vertex angle formed by extending the two sides of an angle in opposite direction"
The property of vertex angle: equal to vertex angle
3、 Vertical
1. Perpendicularity: when one of the four corners formed by two straight lines is a right angle, the two lines are said to be perpendicular to each other. One of them is called the vertical line of the other, and their intersection point is called the perpendicular foot. Mark a ⊥ B
Verticality is a special case of intersection
2. The nature of the vertical line:
① There is only one straight line perpendicular to the known straight line through a point;
② The vertical line segment is the shortest of all the line segments connecting a point outside the line and the points on the line
The length of the vertical line from a point outside the line to the line is called the distance from the point to the line
3. Drawing method: ① one by (known straight line), ② two by (fixed point), ③ three by (vertical line)
4. The vertical relationship of space
4、 Parallel line
1. Parallel line: in the same plane, two lines that do not intersect are called parallel lines
2. "Three lines and octagons": two straight lines are formed by the third straight line
① Apposition angle: "apposition on the same side" means above or below two lines and on the same side of the third line
② Internal stagger angle: "between two sides" is between two lines, on both sides of the third line
③ The inner angle of the same side is between two straight lines and the same side of the third straight line
3. Axiom of parallelism: through a point outside a line, there is and only one line parallel to the line
The corollary of the parallel axiom: if two lines are parallel to the third line, then the two lines are parallel to each other
4. Determination method of parallel line
① Two lines are cut by the third line. If the same angle is equal, then the two lines are parallel;
② Two lines are cut by the third line. If the internal stagger angles are equal, the two lines are parallel;
③ If two lines are cut by the third line, if the inner angles of the same side complement each other, then the two lines are parallel;
④ Two lines parallel to the same line are parallel;
⑤ Two lines perpendicular to the same line are parallel
5. Properties of parallel lines:
① Two parallel lines are cut by the third line, and the same position angle is equal;
② Two parallel lines are cut by the third straight line with equal internal stagger angle;
③ The two parallel lines are cut by the third line and complement each other
6. Distance between two parallel lines: the length of the line segment which is perpendicular to two parallel lines and sandwiched between them is called the distance between the two parallel lines
7. Proposition: the sentence of judging a thing, called proposition, is composed of proposition and conclusion
Five translation
1. Translation: move a figure a certain distance along a certain direction in the plane. This movement is called translation
Note: ① translation does not change the shape and size of the figure, but changes the position of the figure; ② "moving a figure a certain distance along a certain direction" means that "every point on the figure moves the same distance along the same direction", which is also the key to judge whether a movement is translation. ③ the direction of the figure translation is not necessarily horizontal
2. The nature of Translation: after translation, the corresponding line segments and corresponding angles are equal, and the line segments connected by the corresponding points are parallel and equal
It also includes algebra

How to do the last question of Guilin landscape lesson in PEP fourth grade volume 2 Chinese exercise book

Description of the mountain words: towering, Qifeng abrupt continuous
Description of water words: trickle, blue waves, water and sky
I hope I can help you

A number divided by the quotient of 3 and the product of 12, minus 10, the result is 2006, what is the number

（2006+10）÷12×3=504
Have a good time

A batch of washing machines were delivered to the store and sold 24 sets. The ratio of the number sold to the number left is 3 to 5. How many washing machines are there in all?

24/(3/3+5)=64

Practical problems of grade five in Beijing Normal University Edition (2)
Make sure to make a quick decision. After nine o'clock, the problem will be abandoned. If it's OK, there will be a lot of points‘
Tips:
(?) = divided by
X = multiply
= 5/6
1. In order to meet the school anniversary, class 5 (1) has to make 180 small flags, 5 / 6 of which have been made. How many small flags are left?
2. During the May Day golden week, the ticket revenue of star playground on the first day is 960 yuan, which is 6 / 1 higher than that on the second day. How much is the ticket revenue on the second day? How much is the total ticket revenue on these two days?
Remember to answer! Quickly ~

1. In order to meet the school anniversary, class 5 (1) has to make 180 small flags, 5 / 6 of which have already been made. How many small flags are left to be made? (is this 5 / 6
180 * 5 / 6 = 150
180-150 = 30
2. During the May Day golden week, the ticket revenue of star playground on the first day is 960 yuan, which is 6 / 1 higher than that on the second day. How much is the ticket revenue on the second day? How much is the total ticket revenue on these two days? (is this one sixth?)
960 * (1 + 1 / 6) = 960 * 7 / 6 = 1120 yuan
960 + 1120 = 2080 yuan
The next day's ticket revenue is 1120 yuan, the total ticket revenue of these two days is 2080 yuan

10x + 13-x + 9 = (13-x) * 10 + X to solve the equation
Seek the answer! Want the process! Thank you

10X+13-X+9=(13-X)*10+X
10X+13-X+9=130-10X+X
9X+22=130-9X
18X=130-22
18X=108
X=6

There are two rectangular experimental fields, one is 60 meters long and the other is 20 meters wide. The other is 32 meters long and 25 meters wide. 165 kg compound fertilizer is applied according to the area
How many kg of fertilizer should be applied to each of the two experimental fields

There are two rectangular experimental fields a and B, a is 60 meters long and 20 meters wide, B is 32 meters long and 25 meters wide, and 165 kg of compound fertilizer is distributed according to the area. How many kg of compound fertilizer is applied to each of the two experimental fields a = 60 x 20 = 1200 B = 32 x 25 = 800 area ratio = 3: 2 a test

Find a mathematical problem about the circle in the third day of junior high school
In the plane rectangular coordinate system, the circle C with radius r intersects with points D (1,0), e (5,0) on the x-axis and is tangent to the positive half axis of y-axis. Points a and B are symmetrical about x-axis, and point P (a, 0) moves on the positive half axis of x-axis, making a straight line BP, making eh perpendicular to BP and H
(1) Find the coordinates of center C and the value of radius R
(2) The triangle POB and the triangle Phe vary with the motion of point P. if they are congruent, the value of a is obtained
(3) If a = 6, try to judge the position relationship between the straight line AP and the circle C

[solution] (1) let the C coordinate of the center of a circle be (x, y)
R^2=（x-1）^2+y^2=（x-5）^2+y^2=x^2
The solution is: x = 3, y = root 5
R=3
(2) There is △ POB ≌ △ Phe, Pb = PE
OB = OA = radical 5, OE = 5, Op = a, OB ^ 2 + OP ^ 2 = BP ^ 2 = PE ^ 2 = (oe-op) ^ 2,
The solution is a = 2
(3) Given a = 6, the coordinates of point P are (6,0)
Let the tangent at (t is the tangent point) of ⊙ C through point a intersect the positive semiaxis of X at Q. let Q (m, 0), then QE = m-5, QD = M-1,
QT=QA-AT=QA-AB=
From OT2 = OE · OD, we get
∵ a = 6, point P (6,0) is on the right side of point Q, and the ⊙ line AP is away from ⊙ C

The price of a TV set is 1700 yuan, which is 300 yuan less than the original price. How much less?

1700 + 300 = 2000 yuan, 300 divided by 2000 = 15%. A: reduced by 15%