There are also 2 square B-B cube a + 2A square B + AB square 2x + 14 square x-49

There are also 2 square B-B cube a + 2A square B + AB square 2x + 14 square x-49

2 square B-B cube a + 2A square B + AB square
=a（a +b）²/b(a²-b²)
=a(a+b)²/b(a+b)(a-b)
=a(a+b)/b(a-b)
2X + 14 / X square-49
=(x+7)(x-7)/2(x+7)
=(x-7)/2
Please accept the previous one

(- 2A 1 / 2) + (B 2 / 2 a) of the square * a of the square 3B / (- 2A of the square B of the cube) to process thank you

(- 2A, 1 / 2) + (B, 2a), the square of * a, the square of 3B / (- 2A, the cube of square B)
=-1/2a+4a²/b²*3b²/a²÷(-2a²b³)
=-1/2a+12÷(-2a²b³)
=-1/2a-6/(a²b³)

If the x power of 4 = the X + 3 power of 2, then x =? Please
Thank you

From the meaning of the problem, we can get 2 ^ 2x = 2 ^ x + 3, that is, 2x = x + 3 can get x = 3

What is the number at the bottom of the plastic cup 5

Plastic recycling mark
It is said that the plastic products are made of several kinds of plastic products. If the number of recycling materials in each triangle is different, the number of recycling materials in each triangle is different, This set of marks originated in the United States. Now this marking method has been accepted and quoted by many countries, including China. In China, the marking of plastic products with recycling marks is not mandatory. In order to facilitate the recycling of plastic products, some formal big brand enterprises have started to mark recycling marks recently. Although this mark is mainly for the convenience of recycling, But consumers can also know what material the plastic products are made of and under what environment
Different materials use different conditions
The recycling logo on the bottom of plastic products is like a small ID card of each plastic container. They are made of different materials and used differently
"01" - Pet (polyethylene terephthalate)
Mineral water bottles and carbonated beverage bottles are all made of this material. Beverage bottles can't be recycled to hold hot water. This material is heat-resistant to 70 ℃ and is only suitable for warm or frozen drinks. When it is filled with high-temperature liquid or heated, it is easy to deform and some substances harmful to human body are dissolved. Moreover, scientists have found that this plastic product may release carcinogens after 10 months of use, which is toxic to human body, Throw away the drink bottle when it is used up. Don't use it as a water cup or a storage container to hold other things, so as not to cause health problems
Pet was originally used as man-made fiber, film, tape, etc. it was only used in beverage bottles in 1976. Pet was used as filling container, which is commonly known as "Baote bottle". Baote bottle has excellent hardness and toughness, light weight (only 1 / 9-1 / 15 of the weight of glass bottle), easy to carry and use, low energy consumption in production, airtight, non-volatile, acid and alkali resistance, In recent years, it has become an important filling container for carbonated drinks, tea, fruit juice, packaged drinking water, wine and soy sauce. In addition, Baote bottles have been widely used in the packaging of detergents, shampoo, food oil, condiments, sweet food, drugs, cosmetics and alcoholic drinks
"02" - HDPE (high density polyethylene)
The plastic containers for cleaning products and bath products and the plastic bags used in supermarkets and shopping malls are mostly made of this material, which can withstand 110 ℃ high temperature. The plastic bags marked with food can be used to hold food. The plastic containers for cleaning products and bath products can be reused after careful cleaning, but these containers are usually not easy to clean, leaving the original cleaning products, Become a hotbed of bacteria, cleaning is not thorough, it is best not to recycle
PE is the most widely used plastic in industry and life. It is generally divided into high density polyethylene (HDPE) and low density polyethylene (LDPE). PE has excellent resistance to acid and alkali. HDPE has higher melting point and hardness than LDPE, and is more resistant to corrosive liquids. At present, almost all kinds of plastic bags and translucent or opaque plastic bottles on the market are made of PE, Like detergent, shampoo, bath milk, edible oil, pesticide LDPE is ubiquitous in modern life, not because of its containers, but because of the plastic bags you can see everywhere. Most of the plastic bags and plastic films are made of LDPE
"03" - PVC (polyvinyl chloride)
According to reports, the toxic and harmful substances easily produced by this kind of plastic products come from two aspects, one is the monomolecular vinyl chloride that has not been fully polymerized in the production process, and the other is the harmful substances in plasticizers. These two substances are easy to precipitate when encountering high temperature and grease, and the toxic substances are easy to cause cancer after entering the human body with food, Containers made of this material are rarely used for packing food. If used, do not let it be heated
PVC material was invented quite early and widely used in industrial products. Because PVC also has the advantages of other plastic materials, and it has excellent processing and plasticity. In addition, it is cheap and widely used, but mostly in non food areas, such as water pipes, raincoats, schoolbags, building materials, plastic films, plastic boxes and so on, It is mainly used for filling vegetable oil, detergent, pastry box and packaging drinking water. Because the material itself contains chlorine element, it is suspected that VCM monomer is easy to release in the process of bottle making, filling, recycling and reprocessing, which is harmful to human health. In addition, in recent years, with the rising awareness of environmental protection, the industry has gradually changed to other materials for filling containers
"04" - LDPE (low density polyethylene)
Preservative film and plastic film are all made of this kind of material. The heat resistance is not strong. Generally, qualified PE preservative film will melt when the temperature exceeds 110 ℃, leaving some plastic preparations that can not be decomposed by human body. Moreover, when the food is wrapped with preservative film for heating, the oil in the food is easy to dissolve the harmful substances in the preservative film. Therefore, when the food is put into the microwave oven, the wrapped preservative film must be removed first
"05" - PP (polypropylene)
The microwave oven lunch box is made of this material, which is resistant to 130 ℃ high temperature and has poor transparency. This is the only plastic box that can be put into the microwave oven and can be reused after careful cleaning. It should be noted that some microwave oven lunch boxes are made of No.05 PP, but the box cover is made of No.06 PS (polystyrene)), which has good transparency but is not resistant to high temperature, So it can't be put into the microwave oven together with the box. To be on the safe side, take off the cover before putting the container into the microwave oven
PP and PE can be said to be two brothers, but some physical and mechanical properties are better than PE, so bottle makers often use PE to make bottle body, bottle cap and handle with PP with greater hardness and strength. The melting point of PP is as high as 167 ℃, heat resistance, and products can be steam sterilized. The most common bottle making with PP is soybean milk and rice milk bottle, and it is also used to hold 100% pure fruit juice, yogurt, juice drinks, and dairy products In recent years, it has also been widely used to make wash free tableware or wash free cups (used by fast-food restaurants to fill ice products, such as containers used by the popular "quick profit" chain stores). The containers are opaque or translucent, It has the advantages of acid and alkali resistance, chemical resistance, collision resistance and high temperature resistance (about 20 ℃ ~ 120 ℃)
"06" - PS (polystyrene)
This is the material used to make bowl type instant noodle boxes and foam fast food boxes. It is heat-resistant and cold resistant, but it can't be put into the microwave oven to avoid releasing chemicals due to high temperature. It can't be used to contain strong acids (such as orange juice) and strong alkaline substances, because it will decompose polystyrene which is not good for human body. Therefore, you should try to avoid packing hot food with fast food boxes
PS has low water absorption and good dimensional stability. It can be processed by injection molding, compression molding, extrusion and thermoforming. Generally, it can be divided into foaming and unfoamed according to whether it has undergone the "foaming" process. Unfoamed PS is mainly used in building materials, toys, stationery, etc. it can also be made into container filled fermented dairy products (such as Yakult, jianjianjiankang, Duoduo and other dairy products or lactic acid products), In recent years, it is also widely used to make wash free tableware. Foamed PS (commonly known as styrofoam) uses foaming agent to make 20 to 100 times of foam in the manufacturing process. It is used for cushioning packaging materials of household appliances or information items, or ice cream boxes and fish boxes with heat insulation effect, commonly known as EPS (expanded polystyrene). It is also used to make wash free tableware, This kind of styrofoam is usually first made into a flat plate, called PSP (expanded polystyrene paper), and then shaped into various containers. There are also styrofoam molded with food grade EPS, such as coffee cup, shaoxiancao cup, etc
"07" - PC and others
PC is a widely used material, especially in the manufacture of milk bottles and space cups. It is controversial because it contains bisphenol A. experts point out that in theory, as long as bisphenol A is 100% converted into plastic structure in the process of making PC, it means that there is no bisphenol A in the product, let alone release it. However, if there is a small amount of bisphenol A that is not converted into the plastic structure of PC, Therefore, special attention should be paid when using this plastic container
If your water bottle number is 07, the following methods can reduce the risk: do not heat it when using, do not use a dishwasher or a dish dryer to clean the water bottle. Before the first use, use baking soda powder and warm water to clean it, Dry naturally at room temperature. If the container is injured or damaged, it is recommended to stop using it, because if there are tiny pits on the surface of plastic products, it is easy to hide bacteria. Avoid repeated use of aging plastic utensils

Plastic cup, there is a number 58 in the triangle at the bottom of the cup?
I bought a plastic water cup. There's a number 58 in the triangle at the bottom of the cup. What's the meaning? There's a PC beside it
What is the definition of environmental protection index 58? Is the security level very high!

58 refers to the material of PC polycarbonate. The use temperature is - 20 ~ 120 ℃. It's no problem to hold hot water with a good PC, but if the PC is not well processed, it will release bisphenol a when heated. This material is harmful to the body. It's recommended to buy a slightly more expensive cup to use

The bottom of the plastic cup is 5,

Plastic name code and corresponding abbreviation code are as follows:
Polyester-01-pet (Bote bottle)
High density polyethylene-02-hdpe
Pvc-03-pvc
Low density polyethylene-04-ldpe
Pp-05-pp (temperature above 100 ℃)
Polystyrene-06-ps (heat resistant 60-70 degrees, hot drinks will produce toxins, and styrene will be released when burning)
Other plastic codes 07 others
Among them, PP, PE and PVC are abbreviations of English names. The Chinese names are polypropylene, polyethylene and PVC respectively, and the full English names are polypropylene, polyethylene and polyvinyl chloride respectively
"No.1" pet: mineral water bottle, carbonated beverage bottle
Don't recycle hot water in drink bottles
Use: heat resistant to 70 ℃, only suitable for warm or frozen drinks, high-temperature liquid or heating is easy to deform, and harmful substances melt out. Moreover, scientists found that No. 1 plastic may release carcinogen DEHP after 10 months of use, which is toxic to testis
Therefore, the beverage bottle is used