Rational number mixed operation problem, 1 contains addition, subtraction, multiplication and division, 5 in operation. 2 divisor must be negative. 3 calculation result is equal to 2012

Rational number mixed operation problem, 1 contains addition, subtraction, multiplication and division, 5 in operation. 2 divisor must be negative. 3 calculation result is equal to 2012

[4/(-1)+7*7]^2-13=2012
^Represents a power operation

As shown in the figure, the mechanical efficiency of the pulley block is 80% when the pulling force F = 125N and the weight is lifted at a constant speed of 2m within 10s
A. The moving distance of the free end of the rope is 6 MB. The weight of the object is 375 NC. The work done by the pulling force F is 250 JD. The power of the pulling force F is 25 W

A. B, w total = f × s = 125N × 3 × 2m = 750j, w useful = wtotal × 80% = 600J, G object = wtotal × 80% = 600j2m = 300N, so B is incorrect. C, wtotal = f × s = 125N × 3 × 2m = 750j, so C is incorrect. D, P = wtotal t = 750j10s = 75W, so D is incorrect

If the number of items of the arithmetic sequence {an} is odd, A1 = 1, the sum of odd items of the sequence {an} is 175, and the sum of even items is 150, find the tolerance D of the sequence
Hurry up, this is our homework

The number of items of the arithmetic sequence {an} is odd. Let the number of items be 2n + 1. The odd items of the sequence {an} can be regarded as the first item A1, the tolerance is 2D, and the sum of {BN} {BN} with the number of items n + 1 is s = (n + 1) * a1 + (n + 1) * n * 2D / 2 = (n + 1) (a1 + nd). (this is a formula, we must remember) the even items of the sequence {an} can be regarded as the first item A2 = A1 +

When a student rides a bicycle downhill, the distance in the first second is 1 m, the distance in the second second is 3 m, and the distance in the third is 5 m, then the average speed of the bicycle in the first two seconds is 1 m______ M / s, the average velocity in these three seconds is______ m/s．

The distance in the first two seconds is 1m + 3M = 4m, the average speed in the first two seconds is v = st = 4m2s = 2m / s, the total distance in 3S is 1m + 3M + 5m = 9m, the average speed in 3S is v '= s't' = 9m3 s = 3M / s, so the answer is: 2; 3

Xiaoqiang and Xiaogang collect some stamps. After Xiaoqiang gives one sixth of the stamps to Xiaogang, Xiaogang gives one third to Xiaoqiang. At this time, they each have 180 stamps. How many stamps did they originally have? Big brother and big sister help and need it urgently

Xiaoqiang has 108, Xiaogang has 252! Let Xiaoqiang have X, Xiaogang have y, so we can simplify the equations and add the braces of the equations
x+y=360
2/3（1/6x+y）=180
Solution
x=108
y=252

If no matter what the value of K is, x = - 1 is the solution of the equation of X, where two parts of KX + A is equal to three parts of - x-bk, find the value of ab

Put x = - 1 in
Then, we move the items
1-k=-a/2+(-b/3)*k
therefore
-a/2=1
-b/3=-1
The solution is as follows
a=-2
b=3
ab=-6

On the number axis, the point of + 2 is on the () side of the origin, which is () units away from the origin; the point of - 3 is on the () side of the origin, which is () units away from the origin, and the point of + 2 is on the () side of the point of - 3. According to (), we can get - 3 < 2

Right 2 left 3 right small right large

The oil yield of some kind of rapeseed is 33%. How many kilos of rapeseed is needed to extract 100 kilos of rapeseed oil

03 kg, a: 303. 03 kg of rapeseed is needed

3. How to make the operation result 24 (each number can only be used once) by using the mixed operation of - 5, - 12, 7 and rational numbers:

-5-3*（-12）-7=24

One half plus minus one sixth plus minus one twelfth plus minus one twentieth plus minus one thirtieth plus minus one forty second

1/2-1/6-1/12-1/20-1/30-1/42
=(6-2-1)/12-1/20-1/30-1/42
=1/4-1/20-1/30-1/42
=（15-3-2）/60-1/42
=1/6-1/42
=(7-1)/42
=1/7