Able to solve math problems and quadratic application problems. Big brothers and sisters come in

i.e. 1500x 660

Get x 2Set 1 bacterium to reproduce x bacteria in 1 round.

1＋x）²＝256

1＋x|＝16

Get x 15 or x 17 (round).

Then 1 bacterium reproduces 15 bacteria in 1 round.

3.Set the first day to dismantle the x.

1－20％）/x＝1250

Get x 1200

Then on the first day, 1200 was dismantled.

Set the daily acceleration y.

1＋y）²＝1440/1200

1＋y|＝√

y or y house).

then the draw grows approximately every day.

4.Let's grow x every month.

1＋x）²＝

1＋x|＝√

x or x round).

then it grows every month.

1）1+x=

x=2) assumed that x bacteria multiplied on average.

x+1+x（x+1)=256

x1 = 15, x2 = -17 (rounded).

Question 1: 1500 (1 + x) = 1500 + 1500x = 21601500x = 2160-1500 = 660

x=660÷1500＝11/25

Question 2: If a bacterium reproduces a, then there will be a after the first round of reproduction, and there should be a a after the second round of reproduction, that is, a a=256then a=16

Question 3: If b is dismantled on the first day, then b = 1250 (1 20 ) 1200 Let the percentage of daily increase be c, then 1200 (1 c) = 1440 will be solved: |1＋c|then c or c is not possible, then the average daily growth is about.

Question 4: Let the growth of d every month, then 1 (1 x) solves: |1＋d|then d or d is not possible, then it grows every month.

1.Before the discount, it took 1,080 yuan to buy 60 pieces of product A and 30 pieces of product B, and 840 yuan to buy 50 pieces of product A and 10 pieces of product B. After the discount, it took 9,600 yuan to buy 500 pieces of product A and 500 pieces of product B, how much less did it cost than not discounting?

2.A batch of vegetables totaled 140 tons. If it is sold directly in the market, the profit per ton of vegetables is 1,000 yuan; If it is sold after rough processing, the profit per ton of vegetables can reach 4,500 yuan; If it is sold after fine processing, the profit per ton of vegetables increases to 7,500 yuan.

If a vegetable company does rough processing of vegetables, it can process 16 tons back to the state every day; If it is refined, it can process 6 tons per day, but the two processing methods cannot be carried out at the same time, and due to seasonal and other conditions, all the vegetables must be sold or processed within 15 days. There are three schemes: scheme one, all vegetables are rough processed; Option 2:

Vegetables are refined as much as possible, and vegetables that have not had time to be processed are sold directly in the market; Plan 3: Finish some of the vegetables and rough the rest of the vegetables, and complete them in exactly 15 days. Which option do you think is more profitable?

Why dress up?

3.Each iron sheet can make 16 box bodies, or 43 box bottoms, a box body and two box bottoms are equipped into a set of canned food boxes, the existing 150 iron sheets, how many sheets of box body, how many pieces of box bottom, can be just made into a complete set of canned boxes.

Solution: Each piece of children's clothing should be reduced in price

30- )20+8 4 )=800 Note: 8 4: Means 8/4 multiplied

Answer: Each piece of children's clothing should be reduced by 10 yuan

The price should be reduced by X yuan.

30-x）（20+x/4×8）=800

30-x）（20+2x）=800

2x²+40x-200=0

x²-20x+100=0

x-10）²=0

x=10 should be reduced by 10 yuan.

Let the interest on such savings be x

1000[1+(1-20%)x]²=x≈

1) x(13-2x)=20 i.e. 2x 2-13x+20=0 to get x1=4m, x2=

It is 5m long and 4m wide, and if it is 8m wide and long> it contradicts the title.

2) The formula is the same as above, because it is 5m >, so it cannot be enclosed.

3) x(13-2x)= i.e. 2x 2-13x+ Because delta=b 2-4ac = 13 <0, the equation has no solution, i.e. cannot be enclosed.

1。If the length of the bamboo pole is x feet, the width of the door is x-4 feet, and the height of the door is x-2 feet.

According to the Pythagorean theorem there are:

x-2)²+x-4)²=x²

i.e. x -12x + 20 = 0

i.e. (x-2)(x-10)=0

x1 = 2 (rounded), x2 = 10

That is, the length of the bamboo pole is 10 feet.

x1=rounded), x2=

3。Sales in March = 100 (1-20%) = 800,000.

Let's assume that the average growth rate in April and May is x

Then the sales volume in May = 80 * (1 + x) * (1 + x) = that is, (1 + x) 2 =

So 1+x=

x=4.The average annual growth rate is x(1+x) 2=2x=5If you set it to x, it will be 1-x after the first price reduction

After the second price reduction, it is the original (1-x) (1-x) = (1-x) so (1-x) = 1 2

0007.The highest point to 5 m above the water with displacement s =

According to s=1 2 at2

So t=seconds.

8.Let the smaller number be x, 3x -25=(x+2) +x+4) 9.Set the unit digit to.

10.Solution: The price of each shirt should be reduced by X yuan.

40-x)(20+2x)=1200

800+80x-20x-2x2-1200=0x2-30x+200=0

x-10)(x-20)=0

x1=10 (rounded) x2=20

11.Solution: When the selling price is set at x yuan kg, you can make a profit of 200 yuan per day, then:

Meaning from the title: 40(3-x);

Simplification: 50 (x2) + 275x-378 = 0;

Solution: x1=rounded), x2=;

Therefore, when the price is positioned at Yuan kg, it can make a profit of 200 yuan per day, and the price is reduced by Yuan kg).

You can buy in company B: 7500 (800 75%)=, so it is impossible to buy in company B.

Set up in A and buy x units, 800-20x) x = 750020x 2-800x + 7500 = 0

x^2-40x+375=0

x-25)(x-15)=0

x1=25，x2=15

When x1=25, the unit price = 780-20 * 25 = 780-500 = 280<440, rounded off;

When x2=15, the unit price = 780-20 * 15 = 780-300 = 480>440, which is in line with the topic;

I bought it in Company A, and the number was 15 units.

Solution: I bought a set of X in a shopping mall.

(800-20x) x = 7500

800x-20x²=7500

x-25)(x-15)=7500

x1=25,x2=15

When x = 25, 780-20 25 = 780-500 = 280 440 (round).

When x = 15, 780-20 15 = 780-300 = 480 440.

7500 (800 75 ) = 7500 600 = units (house) A: I bought 15 units in a shopping mall.

Solution: 7500 600 = units).

Because it is not divisible, and the more you buy in Company A, the cheaper.

So, buy at least one in Company B and spend 800 x 75% = 600 (RMB).

Set up in Company A to buy x units, then.

x[800 + 800 - 20(x - 1)]/2 = 7500- 600

Solution, x = 69 or x = 10 (undesirable, discarded) 69 + 1 70 (set).

Answer: Buy 1 unit in Company B and 69 units in Company A, for a total of 70 units.

Solution: I bought X in a shopping mall, according to the title.

800-20x）x=7500

800x-20x²=7500

x-25）（x-15）=0

x1 = 25 (rounded) because when buying 25 units, the minimum per unit is 440 yuan, x2 = 15 Answer: I bought it in Zai A shopping mall, and I bought 15 units.

Solution: 1. Let's assume that you can buy it in company B.

n=7500 (800*75%)=Taiwan (not an integer, so excluded)2If you buy it in Company A, it is easy to know that when you buy a unit for 440 yuan, you can buy at least 18 units. 800-20x=440

The total cost is 440 * 18 = 7920 "7500 easy to know that the unit price should be greater than 440, assuming that M units are bought.

m*（800-20m）=7500

m=15 or m=20 (because 20 18, discord with the topic, discarded) So he bought 15 units in Company A.

800*

x=7500 yuanObviously, you can't buy an integer quantity calculator in Company B.

So, I bought it at Company A.

First of all, I think it's better to think for yourself! It's not good to study like this! Ideas:

If you press B, the unit price of 600, 7500 cannot be divisible and rounded! Press A, if there are more than 18 units, press 440 yuan per unit, 7500 cannot be divisible, and it will be rounded off! Therefore, if the number of units to be purchased is x, the price of each unit is 800-20x, and the equation is obtained

800-20x)x=7500, solve x=15 or 25 (rounding) and then answer!

It costs $y to buy x calculators.

Company A y=x(780-20x+20)=20x(40-x), (1 x 18, x is an integer), y=440x (x 19, x is an integer).

Company B y=800*75%x=600x (x 1, x is an integer) If this unit is bought in Company B, then x=, which is inconsistent with reality.

If this unit is bought in Company A and is larger than 18 units, then x = 375 22, which is inconsistent with reality.

Therefore, this unit is bought in Company A and is not more than 18 units.

20x(40-x)=7500

x-15)(x-25)=0

x = 15 or 25 (rounded).

So I bought it in Company B, and the quantity was 15 units.

Let the uphill distance from A to B be x kilometers and the downhill distance is y kilometers, then the flat land is (kilometers, according to the title, x 3 + y 5 + (

x/5+y/3+(

solution, x=, y=

So from A to B uphill, downhill, flat (

Let the corner edge be x-2

The other right-angled side is x

The hypotenuse is x+2

then there is (x-2) 2+x 2=(x+2) 2x 2-4x+4+x 2=x 2+4x+4x 2-8x=0

x(x-8)=0

x=8 so the three sides are 6, 8, 10