There are a few math problems in the first year of junior high school that cannot be written for exp

1, -2a because its opposite number is -a, a-(-a)=2a because a<0 is -2a

2. If c a, the absolute value must be greater than or equal to 0, b is -2a, and if d, it must be <0 to be true.

3, -9 seven-thirds.

Fill in the blank question (1) d a<0, assuming that a = 3, the opposite of a is equal to 3, a minus the opposite of a is 3 3 is equal to 6, i.e. 2a, and the absolute value is equal to 6, i.e. 2a(2) The absolute values of c a and a are equal, and the subtraction is equal to 0I hope you can, I didn't understand the fill-in-the-blank questions, sorry

Multiple choice questions. 1) If a 0, then the absolute value of the difference between a and its opposite is equal to (d) c-a d.-2a Verify that assuming a=-3 then -3-(3)=-6 is 6 in absolute terms

2) The following equation is true for (c).

a.丨a丨+丨-a丨=0 b.-a-a=0 c.丨-a丨-丨a丨=0 d.-a-丨a丨=0

2.Fill-in-the-blank questions.

1) 267 - ( 9 ) = 276 ( 7 3 ) - one-third) = 2

Choice: (1) Because a<0, the opposite of a is -a>0a-(-a)=2a<0, and its absolute value is positive, i.e., -2a. Select D2) a, b, and dValid only when a=0; Select C

Fill in the blanks: (1)-9

2) Seven-thirds.

(5) Ticket fee: 70 60 = 4200 yuan.

The freight shall not be higher than 5000-4200 = 800 yuan, because the number of employees is an even number, then the eleven cars are also an even number, and the remaining number of people can be divisible by 4, then 2 or 6 can be taken

The money used when taking 2: 10 22 = 220 yuan 15 48 = 720 yuan 220 + 721>800 yuan The scheme is not feasible.

As mentioned above, we rent 1 4-seater car and 6 11-seater cars.

2.This year, the peanut yields of the two farmlands are x and y respectively

x (1-80%) + y (1-90%) = 470x + y = 57 solution, x = 20 y = 373Let the speed of trains A and B be x and y respectively

12(x+y)=180*2 60(x-y)=180*2 The solution is x=18 y=12

Let's set the average speed of the train from Beijing to Wuhan is x, and the average speed from Wuhan to Guangzhou is y after the speed is increased, and the total distance is z

2x+50=y

8x+3y=z (3y is 15 hours minus 8 hours equals 7 hours, the title says 4 hours in advance, that is, 7-4=3 hours).

z=15x wish I was right.

(3) The speed of car A is x, and the speed of car B is y

x+y=(180+180)÷12

x-y=(180-180)÷60

x=18 y=12

The speed of car A is 18 meters and the speed of car B is 12 meters and seconds.

The exam is approaching, and it is recommended to classify the practice type questions.

Sales, grasp the formula: selling price - cost = cost x profit margin Generally the cost is x. Then, the quantities that are known and expressed by x are substituted into the formula to obtain the equation.

Sum difference multiplier problem: Set the multiple sentence to x by the quantity before "of", then you can express each quantity, and then use another sentence with an equal relationship, that is, about the sum or difference of two quantities, to list the equation.

Itinerary problem: Remember: The problem of two places meeting in opposite directions at the same time: speed and x time = distance traveled. If it is not at the same time, then remove the time to go first and become simultaneous; If it is not an encounter, then remove the distance of the distance; Make not meeting an encounter.

Chase problem: The difference between the positions of the two cars at the beginning of the chase is the chase distance, then use: speed difference x time = chase distance.

You have to practice a few specific types of questions, and you are familiar with those routines!

1. Set xm fabric for tops, then use 600-xmx 3 2=(600-x) 3 3 for pants

x=360600-360=240（m）

2. Set up a meeting in x minutes.

200x+160x=400

x=10/9

200x-160x=400

x=10

There are 1010 items in total, which are even numbers, so the inversion of the minus and the minus in each parenthesis (equivalent to multiplying by -1) does not affect the plus or minus signs of the final result. Hence the original =

I don't understand it.,It should be very simple.,You might as well send a picture directly.。

Is this a question of the first year of junior high school?

Let's start with the concept of complements: mononomial: 1

The product of any letter and number (in division: dividing by a number equals multiplying the reciprocal of that number). 2.

A letter or number is also called a monomial. 3.The denominator does not contain letters (the mononomial is an integer, not a fraction) a, 5, 1x, 2xy, x 2, are all monomials, where, 2 x is not a monomial.

Polynomial The sum of several monomials is called a polynomial (in subtraction, subtracting a number is equal to adding its opposite). Each monomial in a polynomial is called a polynomial term, and the highest number of these monomials is the degree of the polynomial.

Items that do not contain letters are called constant terms. For example, if the number of the highest term in a formula is 5, and this formula consists of 3 monomials, it is called :

Five triathletes.