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If B has x yuan, then A has (800-x) yuan.

1/4(800-x)-1/5x=56

200-1/4x-1/5x=56

9/20x=144

x=320A: B has 320 yuan.

Let A be x and B be (800-x).

1/4*x-1/5（800-x）=56

Calculated: x=520

So B is 800-520=380

Solution: Let A have x yuan and B have y yuan. According to the title, got.

x+y=800, and.

x/4-y/5=56

Solution, get. x=480, and.

y=320

Solution: If B has x yuan, then A has 800-x yuan according to the topic.

800-x）/4-x/5=56

Solution: x=320

Let A have $ x and B have $ Y.

The system of equations is x*1 4-y*1 5=56

x+y=800

Solution: x=480, y=320

B has 320 yuan.

Let A have x yuan, then.

1/4x-1/5（800-x）=56

Using this equation, you can calculate the money of A, and then use 800-x to get B.

Or, directly, let B have x yuan, then.

1/4（800-x）-1/5x=56

The resulting x is B's money.

If B has x yuan, then A has (800-x) yuan.

So: 800-x) 4-x 5=56

Solution: x=320

That is, B has 320 yuan.

b represents -3, c represents -, point b and point c on the left side of the number line point a represents -2, point d represents, point a and point d are on the right side of the number line 0 in the middle If the origin is changed to point a, what are the numbers corresponding to the other points?

b：-3-（-2）=-1

C:D: When the origin position is changed, does the order in which the numbers represented by the point ABCD are sorted change?

The order of sizes does not change because the order of the points on the number line does not change.

1.Original formula = ab cubic - ab

When a=-2, b=1, the original formula = 2 + 2 = 4

2.The first column is three squares, the second column is two squares, and the third column is two squares.

3.(1) When x=-1, -2a+3b=10, so 3b-2a=10

2) Original formula = 3 (3b-2a) + 2

3x10+2

4.Original = (2007-2004) + (2001-1998) + ....18-12)+(9-6)+3

3x[(2007-9) (2007-2001)+1]+3 code word Qi Xin is not easy, give some points!

Solution: If last year's total investment was x yuan, then this year's total investment was (1 10) x yuan, because last year's profit was 8000 yuan, so last year's total income was (x 8000) yuan, then this year's total income was (1 35) (x 8000) yuan.

Equivalence relation: total investment this year Profit this year = total revenue this year.

1＋10％）x＋ 11800 =（1＋35％）（x＋8000）x=4000

1＋35％）（x＋8000）=

A: Pippi's family's income from pineapples this year should be 16,200 yuan.

If X boxes of A beverages are to be purchased, then (500-x) boxes of B beverages will be purchased from the total cost of purchasing two beverages not exceeding 20,000 yuan.

55x+35(500-x) 20000, solution: x 125 set up the profit of the two drinks in the mall to sell y, then.

y=(63-55)x+(40-35)(500-x)=3x+2500

3 0, y increases with the increase of x, to make y largest, then x should take the maximum value, and the maximum value of x is 125, so when x=125, y obtains the maximum value: 3 125 + 2055 = 2875 yuan.

Set up a type X box for purchase. then type b is 500-x box. Let the profit be y, then the relationship y=x(63-55)+(500-x)(40-35) can be obtained and simplified y=3x+2500

Because the total cost of purchasing two drinks does not exceed 20,000 yuan, 55x+35(500-x) 20,000 solution x 125

Because the coefficient 3 of y=3x+ is greater than 0

So to be y maximum. Then x should be the largest.

x max 125.

y max = 3 * 125 + 2500 = 2875

Therefore, the mall should enter 125 cases of A drinks and 375 cases of B drinks. At this time, the maximum profit is 2875 yuan.

A is x box. Then type B is a 500-x box.

1) y=x(63-55)+(500-x)(40-35)simplificationy=3x+2500

2) 55x+35(500-x) 20000 solution x 125

Because according to (1) y=3x+>0

So to be y maximum. Then x should be the largest.

x max is 125.

So the mall entered 125 cases of A drinks. 375 cases of B drinks.

y max = 3 * 125 + 2500 = 2875

max z=8*x+5*y

55*x+35*y<=20000;

x+y<=500;

x,y are integers;

When the solution is 55*x=20000, the maximum value is obtained, and x is an integer, and x=363, y=1, and the maximum profit is 2909 yuan.

As for the specific process of solving the problem, you can use the ** method, first draw the two straight lines in the constraint (), and then draw the straight line of the objective function (max), and translate the objective function to obtain the maximum value.

Let A enter x box and B enter (500-x) box, that is, 55x+35 (500-x) is less than or equal to 20000, and X is less than or equal to 125. Because box A has a profit of 8 and box B is 15, so y=8x+15(500-x), y=7500-7x, so when x=125, y=7500-7*125=7500-875=6628You can understand the process, right?

This is a linear programming problem.

Solution: Set A to buy X box, B to buy Y box. The profit is z. From the meaning of the title.

x+y=500 ①

55x+35y≤20 000 ②

z=x（63-55）+y（40-35） ③

0≤x≤500 ④

0≤y≤500 ⑤

Then draw the diagram with x as the horizontal axis and y as the vertical axis.

Simplification yields 11x+7y 4 000

Establish a region with , and since the slope of is smaller than , the maximum value is obtained at the intersection of with the x-axis.

and when x = 4 000 7 to achieve the maximum.

Formula x y 3 (1).

x 2y a 3 (2).

Formula 1 + formula 2 gives -y=a

Because x 0 x y 3

So y 3

So 0 y 3

So -3 a 0

Multiply x y 3 by 2 to get 2x+2y=6

The above equation is added to x 2y a 3, 3x = a + 3, x a 3 + 1.

If x>0, then a 3 + 1>0, then a >-3

Bringing x a 3+1 into the first equation gives a 3+1 y 3, y = 2-a 3.

If y>0, then 2-a 3>0, a<6

In summary, -3

Solution: Solved by the system of equations, x=(3-a) 3, y=(6-a) 3x, y are both positive, so x=(3-a) 3>>o

Solution a<3

It's easy!

First establish a coordinate, draw a straight line of x y 3 and x 2y 0, and then translate the straight line x 2y 0, when translating, the x and y in the coordinates are both positive numbers, get two extreme points, find (3,0),(0,3). At this time, the intersection point of the x 2y=z line and the highest and lowest points of the y axis is the range of a-3<=a-3<3, so 0<=a<=6

x+y=3, x=3-y then 3-y-2y=a-3, y= 1 3a then x-1 3a=3, x=3+1 3a

Simultaneous inequality group -1 3a 0, 3+1 3a 0 -9 a 0

Solving the system of equations gives x=(a+3) 3, y=(6-a) 3, because x,y are both positive numbers, therefore,x,y are both greater than 0, and a is greater than -3 and less than 6, i.e., -3 a 6

Sphere volume formula.

v=4/3πr^3

Let the radius of the original jar a, and the radius of the new repair be b, then.

v turns out = 4 3 a 3

v new repair = 4 3 b 3

v original v new repair = 1 8

Rule. 4/3πa^3:4/3πb^3=1:8a:b=1:2

That is, the radius of the newly repaired ball is twice that of the original.

v＝2/3π*r^3

8v＝2/3πr^3

r=2r, i.e. the radius is twice as much.

The cube root of 5x+19 is 4

5x+19=64

x=93x+9=36

The square root of 36 is +6 and -6

5x+19=4 3, the solution is x=9, 3x+9=36, and the square root is plus or minus 6

5x+19=4 to the 3rd power.

5x=64-19

The square root of x=93x+9 is the square root of 36, which is 6 or -6.

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