4 The area of a 18 meter long iron wire enclosing a rectangle twice as long as it is wide

6: 3x+5=0 3x=-5 is substituted into the latter equation -5+2k=-1

7:k=2:8 substitute x=-1 into 2a+3b=c c-2a-2b=0 1 c-2a-3b-1 1=1

8：2a+1=-(1+2a) 4a=-2 a=-1/2

9:8 2*1* =64 You don't have to find 64 (3 2* )=64 9(cm).

10:90*1=90 504-90=414 414 (90+48)=414 138=3 hours.

Therefore, the purchase price of 5 shirts is 60 yuan, an increase of 50% The price is 90, the 20% discount is 72, and the profit is 12

6 If the solution of the equation for x, 3x+5=0, is the same as that of 3x+2k= -1, then k=2

7 The solution of the equation 2ax+3b=c with respect to x is known to be x=1, then |c-2a-3b-1|=1 ．

8 The algebraic formula 2a+1 and 1+2a are inverses to each other, then a=-1 2

9 A long cylindrical test tube with an inner diameter of 3 is filled with water, and the water in the test tube is gradually dripped into a cylindrical glass with an inner diameter of 8 and a height of 1 8, and when the glass is filled with water, the height of the water in the test tube drops by 64 9

10 The Chengdu-Chongqing Railway is 504 km long An express train departs from Chongqing at a speed of 90 km/h, and one hour later, another slow train departs from Chengdu at a speed of 48 km/h, and the two trains meet three hours after the slow train departs

10. The total length of the Chengdu-Chongqing railway is 504 km, with the speed of express trains being 90 km/h and the speed of slow trains being 48 km/h.

Set t hours after the two cars meet, at which point the distance between the two cars is equal to the distance between the two places.

1+t)*90+48t=504 t=3

That is, the two cars met after 3 hours

9 According to the theme, the water level of the cylindrical long test tube with an inner diameter of 3 drops by h centimeters, so that the inner diameter of 8 and the height of 1 8 cylindrical glass cups are filled.

1 4*pi*3 2*h=1 4*pi*8 2*h=When the water is full, the height of the water in the tube decreases

8.2a+1=-(1+2a) then a= -1 2

According to the theme, the length of the rectangle is 2x meters, and the width is x meters, then: the branch bark is 2x+x=9, the solution is x=3, 2x=6, and the area of the rectangle is: 6 3=18 meters 2

Width = 18 2 (2+1) = 3

Length=3 2=6

Area = 3 6 = 18 (square centimeters).

The width of the bend is carried simply, and the length is x, and the length is y

xy=24y=2x-1

x(2x-1)=24

2x²-x=24

2x²-x-24=0

x=1 (1+192) 4

Because x 0 so x = 1 + root number 193 4

Solution: If the width is x cm, the length is an empty spike hole (2x-1) cm, and the title is dry.

2（2x-1+x）＝24

Solution. x＝13/3

That is, the width is 13 3 centimeters, and the length is 2 13 3-1 = 23 3 centimeters.

Summary. The length is a multiple of the width, and the height is a multiple of the width, where the width is the unit one, the length is the multiple unit 1, and the height is the multiple unit one, so the length is widened and heightened, and the total length is length, width and height = edge length and 4

With a 148 cm long Xianghe Li wire enclosed into a cuboid, patting wax to make the length of the delay is a time of width, height is a time of width, and what is the volume of the rectangular area?

The area is 900 square centimeters, and the volume of the body is 1800 cubic centimeters. Equation: 148 4=3737 (

The length is a multiple of the width, the height is a multiple of the width, the width of the potato mill is a unit one, the length is a unit 1, the height is a multiple unit one, so the length is wider and taller, a total of length and width and height = edge length and 4

Surface area = (length and width + width and height + height and length) 2 volume = length and width and height.

The width of the solution is x centimeters, and the length is (2x) centimeters.

2x+x）×2＝18

3x＝18x＝6

The length is vertical rent: 2 6 12 (more than a trillion centimeters) such as resistance.

Area: 6 12 72 (cm²).

Let the width of the long core spike square be xm, then the length is 2xm, and the root Yun Shi according to the title of the Pon's quarrel obtains: 2 (x+2x) = 18, the solution: x=3, the area of the rectangle is: 3 6 = 18 (m2, A: the area of the rectangle is 18m2

This is a typical harmony problem.

The length and width are known to be:

160 2 = 80 meters.

The difference between length and width is: 18 meters.

By the sum difference problem formula:

The length of the rectangle is: (80+18) 2=49 meters.

The width of the rectangle is: (80-18) 2=31 meters.