The questions of the second year of junior high school are urgent, and the questions of the second y

1) What kind of purchase plans does the company have?

2) What kind of purchasing plan the company adopts to obtain the maximum profit What is the maximum profit.

3) If you purchase again with the profit obtained in (2), please write the purchase plan to maximize the profit.

Idea Analysis:"Purchasing plan"In essence, it refers to the allocation of 20 pieces of goods A and B into A, and how many pieces of B have several allocation methods, so the number of pieces of any commodity A or B is x, and the number of pieces of another commodity is obtained from the total number of pieces; By listing the inequality group by the funds, you can find the value range of the number of pieces x, and then find the functional relationship between the profit and the number of pieces, and then apply the function properties or substitute verification to find the maximum value of profit and the design scheme.

Solution: (1) Set up the purchase of X pieces of product A and 20-x pieces of product B

190≤12x+8(20-x)≤200

Solution: Because x is not a negative integer, x can be taken as 8, 9, and 10

Therefore, there are three purchase plans: purchase 8 pieces of product A and 12 pieces of product B.

9 items of product A and 11 pieces of product B were purchased.

Buy 10 pieces of product A and 10 pieces of product B.

2) The profit of each piece of commodity A is 10,000 yuan.

The profit of each piece of commodity B is 10-8=20,000 yuan.

Method 1: Profit w=

w is a primary function of x, and the coefficient of x is 0, so w increases with the increase of x.

Therefore, when x is a maximum value of 10, w has a maximum value of 45

Method 2: (1) The profits of the three schemes are 440,000 yuan, 10,000 yuan, and 450,000 yuan respectively, so when you buy 10 pieces of product A and 10 pieces of product B, you can get a maximum profit of 450,000 yuan.

3) If you buy 1 product A and 4 products B, you can get the maximum profit.

Important reminder: This question involves four quantitative relationships: the number of goods A + the number of products B = the total number of pieces, the number of goods purchase price = total price, selling price - purchase price = profit of each product, profit of each product number of goods = total profit; At the same time, pay attention to figuring out which quantities are known, which quantities can be used in algebraic tables, and have more data to prevent confusion.

A company operates two kinds of commodities, A and B, with a purchase price of 120,000 yuan and a selling price of 10,000 yuan; The purchase price of each B product is 80,000 yuan, and the price is 100,000 yuan, and their purchase price and selling price remain the same. Now it is ready to purchase a total of 20 pieces of A and B, and the funds used are not less than 1.9 million yuan and not more than 2 million yuan.

1) What kind of purchase plans does the company have?

Solution: If product A enters x pieces, then product B enters (20-x) pieces.

190 ≤ 12x+8(20-x) ≤200190 ≤ 4x+160 ≤ 200

30 ≤ 4x ≤ 40

x ≤ 10

x desirable, three kinds.

So there are 3 kinds of purchase plans, which are:

8 pieces of A and 12 pieces of B, 1.92 million are needed.

9 pieces of A and 11 pieces of B, which require 1.96 million.

10 pieces of A and 10 pieces of B, 2 million are needed.

2. What kind of purchasing plan does the company use to get the most profit? What is the maximum profit?

Solution: Profit (

It can be seen that the greater the x, the greater the profit.

Therefore, choose the third option, that is, 10 pieces of A and 10 pieces of B, to get the maximum profit.

The maximum profit is 10,000.

3) If you purchase again with the profit obtained in (2), please write the purchase plan to maximize the profit.

Solution: Let A enter x pieces, and B enter Y pieces.

12x＋8y≤45

x can have four options.

x 0, y 5, profit 100,000.

When x 1, y 4, the profit is 10,000.

x 2, y 2, profit 90,000.

x 3, y 1, profit 10,000.

So the way to get the maximum profit is: 1 piece of A, 4 pieces of B.

According to the title, "the width around the area is the same", it can be seen that drawing a small rectangle is equivalent to leaving a small rectangle with the same width (x) around the original rough rectangular open space. (The four corners are all small squares with x as the side length).

Solution: Let the length of the small rectangle be a and the width be b

The missing area of a small rectangle is s=24 12 (5 9)=160 square meters.

After the above analysis (drawing more clearly), it is known that the length of the small rectangle is 24-2x, and the width is 12-2x

s=ab=（24-2x）×（12-2x）=160x^2-18x-8=0

Solution: x=(18+ 356) 2

a= ;b=

The length of the small rectangle is meters, and the width is meters.

The method is a stool line that is not wrong, why is it a negative value to be solved, should there be a problem with the question???

Move 4ab to the left of the equation sail and break it down to get:

a 2b 2-2ab+1]+[a 2-2ab+b 2]=0, so (ab-1) 2+(a-b) 2=0

If the sum of two squares is equal to zero, then both are zero.

So: ab-1=0

a-b = 0 solution equation Bu Qing hail group.

a=1；b=1

or a=-1;b=-1

a-2b) positive chain +(b+1) +99

The square is greater than or equal to 0

So when a-2b=0, b+1=0

That is, when a = -2 and b = -1, a is a minimum = 99

1.The square of a is multiplied by the square of B + the square of a + the square of B + 1 = 4ab, and the value of a and b is obtained.

The original formula can be turned into.

ab-1)²+a-b)²=0

So ab=1, a=b

So a=1, b=1 or a=-1, b=-1

2.The minimum value of the square of the algebraic formula a + 2a + 3 is ( 2 ) [without process] find the square of a = a + the square of 5 times b - the minimum modified hidden value of 4ab + 2b + 100.

The original formula can be turned into.

a-2b)²+b+1)²+99

The minimum value is 99

1.(a^2b^2-2ab+1)+(a^2-2ab+b^2)=0ab-1)^2+(a-b)^2=0

ab=1 a-b=0 a=b=1 or a=b=-12Minimum pickpocketing value = 2

The square of the square + 5 times b is -4ab+2b+100(a 2-4ab+4b 2)+(b 2+2b+1)+99(a-2b) 2+(b+1) 2+99

The minimum value is 99

The first question, a convex lens is facing the sun, so as to form a brightest, the smallest point, take out a measuring stick to measure the distance from the point to the convex lens, that is, the focal length of the convex lens.

The second question, advocacy:1. Preservation method 1 Preservation method 2 Preservation method 3: Fresh meat, canning method, freezing method, vacuum packaging method.

Fresh milk, pasteurization, freezing, vacuum packaging.

Apples canned method, air-dried method, vacuum packaging method.

Soybeans, air-dried, canned, frozen, and the little messenger of peace, from a small family to the people around him, the society advocates peace.

Question 3: Disagree. Because expired yogurt contains a lot of bacteria and fungi, it can produce toxic substances over time.

Over time, other bacteria will also breed, and the yeast will become ineffective if it is not a sclerotinia fungus.

The first question is to put a convex lens facing the sun, so as to form a brightest and smallest point, and take out a measuring stick to measure the distance from the point to the convex limb lens, which is the focal length of the cavity convex lens.

The second question is to be a small envoy who advocates peace, and advocates peace to the people around him and the society from small things.

Well, I'm not very good at biology, so ask someone.

Physics: Use a point light source, move on the main optical axis, when it becomes a parallel light, measure the distance from the point light source to the convex lens, that is, the focal length of the convex lens.

The original operating speed is x kilometers per hour.

Rule. 312/x=154/

After Xie Xianheng came out of X, he just took his brother to do Lu Liang.

80 km/h.

Let the current velocity be v, then the original Zen cong cha velocity is v; Now the required time is t, then it is t+

Binary Equations: Zheng Qiao.

vt=154

v gets v=80

A to BC to make a high ah, ABCH four points of the circle, and then prove.

Xiaoliang's typing number: (1+1 3)a=4a 3

Xiaoliang's typing speed = Xiaoliang's number of typing Xiaoliang's time.

1+1/3）a÷(2n/3)

4a/3÷2n/3

2a/n