hh, help with this math problem

40 2 = 20 (cm) (the length of the sides of a square).

20x20 = 400 (square centimeters).

The surface area of a cube is calculated as side length*side length*6

Therefore, if the original side length is x, then (x+2)*(x+2)*6 - x*x*6 = 40

Calculate x=2 3

Therefore, the surface area is 8 3

Let the original side length of the cube be x, and the solution is: 6*(x+2) 2 -6* x 2=40, and x=2 3, so the area of the cube is: 6*(2 3) 2=8 3

Solution: Let the side length of the cube be x

6（x+2）^2-40=6x^2

6（x^2+4x+4）=6x^2

6x^2+24x+24-40=6x^2

24x=16

x=2 3Because the cube side length is 2 3, the surface area of the cube is 6 * 2 3) 2 = 8 3 square centimeters.

That's how it should be.

Suppose the original cube is x in length, so the original cube surface area is: 6x the length is increased by 2, so the surface area is now: 6(x+2) so there is: 6(x+2) -6x = 40

Solve x, x=2 3

Therefore, the surface area of the metacube is: 6*4 9=8 3The surface area of the cube after growth is: 6*(2 3+2)=128 3

Because (2k+2) 2-(2k) 2=4k 2+4k+4-4k 2=4k+4=4*(k+1), the mysterious number constructed by the sending roller die with two prepared dust slow continuation even numbers is a multiple of 4.

Solution: (1) Let p(x0,y0).

2) Let the straight line pm be y=k(x+1).

k(1+1)-0|Under the root number (1+k) = root number 2 solution: k = 1 k = 1

y=±x±1

3) The distance from the center of the circle (3,0) to the two straight lines is.

3+1-0|Root number 2 = 2 root number 2 = r satisfies , p(1,2)|-3-1-0|Root number 2 = 2 root number 2 = r satisfies , p(1,2)|

AOC and COB are adjacent complements.

aoc+∠cob=180°

OD is the angular bisector of AOC and OE is the angular bisector of COB.

2∠doc+2∠coe=180°

doc+∠coe=90°

doed=90°

There are at least 176 trees.

Solution: Suppose there are x trees, y people.

Then 4y+32=x can be listed according to the previous list

In the last sentence, if each person plants 5 trees, and the last person has planted trees, but there are less than 3 trees, so the last person can only plant 1 or 2 trees, and the question asks at least how many trees, so it can be listed according to 1 tree.

5（y-1）+1=x

According to the system of equations, x=176, y=36

So there are at least 176 saplings in this batch.

If there are as few trees as possible, then it is the last tree planted by the last person, as little as possible, because it has tree species, there are less than three, so he can take one or two when the number is less, that is, he only planted one tree, and at this time there are 176 trees in total.

Subtract the total distance from the time it takes for the express train to go ahead and divide by the sum of the speeds of the two cars to get the answer:

300-1 4*60) (60+40) = Analysis: When they set off at the same time, the actual distance should be the total distance minus the distance of the express train first, and then the two cars should walk in opposite directions, and their actual speed should be the sum of the speeds of the two cars.

Divide the total distance by the difference in speed between the two cars and you get the answer:

300/（60-40）=15（h）

Analysis: When the fast car is chasing the slow car, the slow car is also getting rid of the fast car, so their actual speed should be the difference between the speed of the two cars. The fast train starts 300km behind the slow train, so just divide the total distance by the total time.

Let the fast train meet after x hours, and the slow train meet after y hours x-y=

x*60+y*40=300

y=x=3 hours and 6 minutes after driving.

Set the fast train to catch up with the slow train after X hours.

60*x-40*x=300

x = 15 hours.

x-y=

x*60+y*40=300

y=x=A: Meet after 3 hours and 6 minutes.

Set the fast train to catch up with the slow train after X hours.

60*x-40*x=300

x = 15 hours.