Mathematics around me, whoever has 30duo can do it! Rush Rush

Think for yourself, don't ask Dad.

3、a4、d

5, a6, [-1,1], the second one seems to have a problem.

7、e^(-2)

dx/(1+4*x^2)

What about the title??? Where is the topic?

Send it one more time.

Got a problem? I didn't see it.

2a b+2ab-4a b =-2a b+2ab When a = 1, b = -1 substitution = 2 times 1 times -1 times -1 + 2 times -1 times 1 = -2 + (-2) = -4

？？？How do you evaluate an equation without an equal sign?

1 The product of the maximum and minimum two numbers is an odd number, and both numbers are odd numbers.

If the sum of the four numbers is 11, then let the maximum number be x, x-4 + x + the middle two numbers = 11 If the minimum number is 1, then the maximum number is 5, and the remaining two numbers are 2, 3 If the minimum number is 3, then the maximum number is 7, and the sum of the remaining two numbers is 1, so the four numbers are 1, 2, 3, 5

Their product is 1*2*3*5=30

2 Suppose the truck speed is x km/h.

then (6+1)*40+x=6*52

Solve the equation to obtain: x=32

3 7 mantissa is 7

The mantissa of 7*7 is 9

The mantissa of 7*7*7 is 3

The mantissa of 7*7*7 is 1

The mantissa of the product of five sevens is 7

The product of six sevens has a mantissa of 9

Therefore, it can be seen that the product mantissa of 7 is 4 cycles.

2005 sevens multiplied by (501*4+1) 7s multiplied 4 cycles after 501 cycles and then back to the first one, so the mantissa is 7

I hope it helps you, and I do it all by myself.

If you don't know or don't understand, you can ask! I hope you adopt me hehe

1.Because the smallest two-digit number is 10, the sum of these four numbers is 11, so the smallest number can only be 1, otherwise the sum must be greater than 11.

Then the largest number is 5, because the sum of the four numbers is 11, so the sum of the middle two numbers is 11-1-5=5, so it can only be 2 and 3

Therefore, the product of the four numbers is: 1*2*3*5=30

2.The distance between vehicle A and workshop B when it encounters a truck coming from the opposite side is: (52-40)*6=72 kilometers.

Car B also met the truck 1 hour later, indicating that the two cars had traveled a total of 72 kilometers in 1 hour, so the speed of the truck was:

72-40*1) 1=32 km/h.

3.Since every 4 27 multiplied mantissa is 1, in 2005 there is a total of: 2005 4 = 501... 1

and 501 4 surplus 1

Therefore, the mantissa of the product of 2005 27 consecutive multiplication is 7.

If you don't know, ask again.

The four numbers in the first question are 5 3 2 1 I don't know if it's right

Let ABCD be four letters, the largest is a and the smallest is D

The difference between the largest number and the smallest number is equal to 4"a-d=4, because "the sum of the four numbers is 1 more than the smallest two-digit number" and the smallest two-digit number is 10, which is 1 more than it, so a+b+c+d=11, a-d=4" can be brought in from 9-5, 8-4, 7-3, ,..However, if the maximum and minimum are all greater than 11 after summing, it is obvious to exclude, so 6-2 = 4 or 5-1 = 4 or 4-0 = 4 is obtained

Because "the product of the largest number and the smallest number is an odd number" so only 5-1 = 4 matches, 5 is the largest, 1 is the smallest, then the number between 1 and 5 has three numbers. "a+b+c+d=11" gives b+c=5, so it is 2+3=5.

The last four numbers are:

No, the second question, I haven't learned the application questions of the encounter problem since I was a child.

The third question should only look at the mantissa number, 7 7 = 49. Mantissa 9, 9 7 = 63, mantissa 3, 3 7 = 21, mantissa 1, 1 7 = 7, so that a cycle is formed. 7 times will appear in 4 times, so the head is calculated, and it is concluded that 2005 times divided by 4 is equal to 501 and more than 1 time, so the answer is 7

1.Let these four numbers be a, b, c, and d from small to large, and we can get according to the conditions:

The difference between the maximum number and the minimum number is equal to 4 ==》d-a=4;

The product of the largest and smallest numbers is an odd number ==》A and d are both odd numbers;

The sum of these four numbers is 1 more than the smallest two digits ==》a+b+c+d=11 (it can be seen that a, b, c, and d are all numbers less than 10);

There are 1,3,5,7,9 odd numbers within 10, and if we assume a=1, then d=5, and according to the sum of 11, we can get b+c=5, so b=2, c=3;Thus the four numbers are 1, 2, 3, 5, and the product is 30.

2.When the truck and car A meet, A and B are separated by s=52*6-40*6=72km, and the truck and car B meet in 1 hour, indicating that the sum of the distance traveled by the truck and car B is 72km in this 1 hour, and the truck speed is v, then 40*1+v*1=72, v=32km h can be obtained.

3.Only the mantissa multiplication can be found that the mantissa of 7 * 7 is 9, the mantissa of 9 * 7 is 3, the mantissa of 3 * 7 is 1, the mantissa of 1 * 7 is 7, and then the mantissa of 7 * 7 is 9, it can be seen that the mantissa is 9, 3, 1, 7 cycle, 2005 27 multiplication can be written as (27 * 27 * 27 * 27 * 27) to the 401st power, so the mantissa is 7.

1. According to the sum of the next four numbers is the smallest, it can be considered that these four unequal natural numbers are ......and so on.

Because the product of the minimum and maximum numbers is an odd number, both the maximum and the minimum numbers are odd numbers, so the minimum number can be determined to be 1

However, it can be determined that the maximum number is 1+4=5

Thus, the other two intermediate natural numbers are two of , which, according to the title, take their smallest 2 and 3.

So, the minimum sum of these four numbers is 1+2+3+5=11.

2. 6 hours after the departure of A and B, A and B are 6 72 kilometers away from each other, A meets a truck, and 1 hour later, B meets a truck, which is equivalent to transforming the problem into "B and the truck are 72 kilometers away, going in the opposite direction, and meeting ...... 1 hour later

So the truck speed 72 40 32 kilometers per hour.

The number of digits of the multiplication product is , that is, 2005 4 is more than 1, then the mantissa of the product of 2005 27 consecutive multiplication is 9

1.There is a problem in the first question, how can a sum of four numbers be 1 more than the smallest two digits???

After hours, the two cars are 72 kilometers apart, and the truck speed is x, then (40+x)=72, so the truck speed is 30 kilometers per hour.

3.This title is to find the law, that is, 2005 7 multiplication to see the mantissa number, its cycle period is 4, respectively, a total of 501 cycles, the last one is 7, so the mantissa is 7

Hope my answer will help you.

(The mantissa of 4 multiplied by 27 is 1, and the mantissa multiplied by 1 is always 1, so the mantissa of 2004 multiplied by 27 is 1, and the mantissa of 2005 is 7).

Extend the two bus bars to A, the height of the large and small cones, O1O2 = 2 2, O1C = 2 2 = 1, O2B = 6 2 = 3, A2 = A1 + 2 2

The triangle ao1c is similar to the triangle ao2b, ao1 (ao1+2 2)=1 3,,3ao1=ao1+2 2,ao1= 2,ao2=3 2, the original cone is a large cone, and its volume v=1 3 *3 *3 2=9 23 2.