A series of math problems. A math problem

1) I didn't understand.

2）15x+5+6＜4x-6x-6

15x+11＜-2x+6

17x＜-17

x -1x+1 0 after removing the absolute value - (1+x) x 0 after removing the absolute value - x

丨x+1丨-丨x丨=-(1+x)-(x)=-13) 2x-4y=6a-4

x+2y=5a

The value of x=4a-1 y=1 2a+1 2x is 3 times the value of y, 3 (1 2a+1 2)=4a-15 2a=-5 2, and the solution gives a=1

4) Dissolution: (55+1) 3=22

55+2) 5=11 remainder 2

then up to 37 eggs.

5) x and y are inverse numbers x=-y

Substituting the system of equations x-5y=2m, 2x+7y=m-186y=2m, y=-3 m, x=3 m

6）.Suitable for x+y=3 so that x=1, then y=2

Substitut the equation 2x+2y=2k+3

2+4=2k+3

k=3 27) Train speed: 200 40=5m s bridge length 5*60=300m

8) The unknown hundred should be listed as a binary one-dimensional equation solution.

9) The solution set of a(x-1)>x+1-2a is x<-1ax-a x+1-2a

a-1）x＞1-a

a-1＜0 x＜（1-a）/a-1

1-a）/a-1=1

a=110) solution: answer x question correctly, choose wrong or not choose inverted y question.

x+y=25 10x-5y=200

The solution is x=15 y=10

He answered at least 15 questions correctly.

11) 3x+y=1+3m x+3y=1-mx=(2-6m) 8 y=(2+10m) 8x+y>0 (2-6m) 8 +(2+10m) 8 0 solution m 112)3k-5x=-9

The solution of x=(3k+9) 5 is a non-negative number.

3k+9）/5≥0

k -313)2x-a<-1 x-2b>3 to get 2b+3 x (a-1) 2

The solution set is -12b+3=-1

a-1/2=1

The solution is a=3 b=-2

a+1)(b-1)=(3+1) (2-1)=-12 to get x -2 3

The other solution yields 2(2x+1)-3(1-x) 67x 7 x 1

2/3＜x＜1

15) No! It's also a system of binary equations.

16) Set the waist length of the triangle x the bottom length y

x+x/2=15 x/2+y=6

x=10 y=1

17) That inside angle and formula I forgot.

18) Forgot.

19) BAC = 180-75-45 = 60° AE bisect BAC BAE = 30° BAD = 90-75 = 15° DAE = 30-15 = 15°

aec=75+30=105°

It's so hard! Give more points!!

Big brother, you're really slamming the door, even if you know how to do it, you're not in the mood to watch it.

Well said upstairs, top! Who would read such a long question?

How many kilograms does a bundle of wire weigh?

You didn't say all the questions, and you didn't say how many kilograms of wire the school bought. Since the wire is homogeneous, we see it as a cylinder of uniform density, so its weight is proportional to its length, i.e. the weight per unit length is a constant. So there is the weight of the whole bundle of wires The length of the whole bundle of wire=

I don't know how many kilograms it weighs in total, how to calculate it? If x kilograms, the equation is as follows: x (

This is a permutation problem.

are evenly put.

Therefore, if the probability of touching a hundred is 1 3, then the probability of touching the red ball is 2 32A ball touched with a return indicates that the event is an independent event that compensates for the probability of affecting other balls, so the probability of hitting a red ball each time is 1 3

Multiply the permutations and combinations of independent events by the probability formula for each time as c5 3 (that is, the representation of permutations and combinations, I use this here: 5 is below c, 3 is above c).

c5 3 times 1 3 to the third power and then multiply 2 3 squared to get the result 40 243, the probability answer to the first question is 40 243

The first touch means that the probability of the first time is determined to be 1 3, so that is to say, the color of the first touch ball is red and white. To put it simply, you can touch any ball, so obviously the probability is 1 (100%)

Therefore, the formula of the second question is 1 3, and the cubic of 3 gives 1 27, and the probability answer of the second question is 1 27

If there is something that helps you, please take it if it is convenient for you. Thank you.

A is in it, B is not.

It's B, and A doesn't.

Yes (so the probability is.)

Thus, if the last difference in line n*(n+1) 2 is a number, then the last number in line 20 is -1 200, and the tenth imaginary number in line 20 is -1 200, which is negative.

Regardless of the plus or minus signs, it is clear that odd numbers are negative and even numbers are positive.

By observing one number in the first row, two numbers in the second row, and three numbers in the third row...

It can be found that the last number in the nth row is dust n*(n+1) 2 (1+2+3+4.). And bent eggplant. formula).

Therefore, the last number in line 19 is 19*20 2=190, and the 10th number in line 20 is 190+10=200, which is positive because it is an even number. The question is a fraction, so it's 1 200