Ask a high school math problem, not very understanding

<>a(6,6) is 6 balls that are placed in any numbered box.

a(5,5) A is put in box No. 1, and a(5, 5) B is put in box No. 6, to be subtracted, but.

a(5,5) A is placed in box 1, which contains the case that A is placed in 1 and B is placed in 6.

a(5,5) B is placed in box 6, which contains the case that B is placed in 6 and A is placed in 1.

That is to say, A is put to 1, B is put to 6 minus twice, so it is necessary to add one more subtraction, A to 1, B to 6 = a(4, 4).

So get the results on the book.

2.If you want to choose three people, and if you want to choose A and B, you can choose one person from the remaining 8 people, so it is C(8,1).

Total = c(10,3).

1 The first one is minus twice Party A 1 li, B also puts 6 li in other random rows of all the arrangements - A in the first (note: including A in the first number, B in the sixth + A in the first number, B is not in the sixth number) - B in the sixth number (note: including A in the first number, B in the sixth + A is not in the first number, B is in the sixth number) + A is in the first number, B is in the sixth number.

2 also counts because the denominator is all combined.

The numerator should be two definite people, one random, so one of the eight is also one of the eight combinations.

If this step is missing, the molecule will only have one combination, which does not correspond to the actual situation.

The first one thinks that your reduction of A55 includes for example, Party A 1 mile, and B also puts 6 miles. B is placed in 6 miles, and Party A is 1 mile, which is repeated and subtracted 2 times, so it has to be added.

Yes, because there are 8 different options to choose after choosing A and B.

1) The book is right, you build two A55, and the A in it is in 1 and B is in 6, and you subtract it twice, so you have to add it back once!

If there is a problem with the answer input, delete the =f(x) line. Multiply the top and bottom by 2 to the x power at the same time to simplify.

The analysis here has been made clear, and the problem can be solved by the definition of an odd function.

This question is actually to examine the positional relationship between a straight line and a circle.

You can think of x 2+y 2=r 2 as follows: when the circle x 2+y 2=r 2 intersects with the line x+y=1, find the minimum radius and get the x 2+y 2 minimum.

He understood it to mean , because x 2 + y 2, represents the square of the minimum of the distance from the origin o to the point p on the line l. The expression is x 2 + y 2 = op 2

Why is p a point on l?

ans: It's hypothetical, specifically:

Let p(x,y) be a point on a straight line l, and x 2+y 2=op 2 is not a circle?

ans: x 2 + y 2 = op 2 is good, but the geometric meaning of x 2 + y 2 here is: the sum of the squares of the distance from a point to the origin on a straight line;

The geometric meaning of x 2+y 2 under the root number comes out, it is the distance from the moving point to the origin point on the straight line, your answer is yes, I won't give you the solution here, the minimum value of op is: root number 2 2

The minimum value of OP2 is 1 2;

The answer is one in two;

If there is anything you don't understand, ask again

x+y=1, so: y=1-x

x^2 + y^2 = x^2 + 1-x)^2 = x^2 + 1 - 2x + x^2 = 2x^2 - 2x +1

The one above is a quadratic equation. How to find its minimum value, you know?

x 2 +y 2 can be understood as the square of the distance from the point to the origin. (It can be said to be a circle, but if you want to go deeper, what is the definition of a circle, and how far is it from point to point......Then x+y=1 is a straight line, and there are infinitely many points on the line, one of which is closest to the center of the circle.

So the problem is reduced to a point-to-straight distance.

If it is too annoying to use pure algebra methods, it is easier to understand the geometric meaning, and it is better to draw a diagram to do geometric meaning questions.

An empty set is a set that does not contain any elements, it is contained in any set, and it is a subset and a true subset of any set.

Bring in 1, solve a=-3, and solve the set a= equation to get x=1, x=-1 3

I forgot a little about the expression of the a=enumeration method, but you should understand the general meaning.

An empty set is a set without elements, i.e. nothing, empty. An empty set is contained in (0,1,2), and an empty set is contained in any non-empty set.

Substituting x=1 into the square of ax + 2x + 1=0 gives a=-3 and then solves the equation -3x 2+2x+1=0 to get a=

(1) The value range of the angle between two straight lines: (0,90】(2)The value range of the angle formed by the straight line to the straight line:(0,180)(3)The value range of the angle formed by two straight lines of different surfaces:

0,90](4)The value range of the angle formed by the two vectors:[0,180](5)The value range of the angle formed by the straight line and the plane:[0,90](6)The value range of the angle formed by the plane and the plane:

0,180] unit: °

Except for the vector which is 0 180 and the others are 0 90, the opening and closing intervals do not need to be mastered.

An ellipse can be made after each point p, and its major axis may be different, with one ellipse having the shortest major axis. According to the nature of the ellipse, its major axis is the sum of the distances from p to the two foci, so the shortest major axis is the point where the sum of the distances from the two foci is found in the given line.

This problem is equivalent to picking up water from place A to the river to place B, finding the water intake point with the shortest water carrying path, and using the river as the axis of symmetry to make a mirror image of AB.