The second question of mathematics why k 2 3 2 is a bit difficult to figure out here, ask for a deta

When the axis of symmetry is (1+2) 2, i.e., 3 2, a1 is equal to a2. When it is less than 3 2, a1 is less than a2

Let's bring in and count:

We need to satisfy (n+1) 2+k(n+1)+4-n 2-kn-4>0 simplified 2n+1+k>0

For k to be true for all positive natural numbers, of course we have to consider the critical case:

When n is the smallest, 2n+1+k must be true.

The smallest n is 1, then 3+k>0 must be true, so the answer comes out.

What is the teacher's method? The teacher's approach is considered from the point of view of functions! Assuming that n + kn + 4 is a function, then to satisfy a>a, it is also necessary to satisfy at most from 2, and the function begins to increase monotonically).

The function is a quadratic function with an opening upward, the axis of symmetry is x=-k 2, and the right side of the axis of symmetry is monotonically increasing. The critical case is: n=2 begins to increase monotonically, and n=1 satisfies a>a, although it is on the left side of the axis of symmetry.

When the axis of symmetry is 3 2, f(1)=f(2)=2, so we require the axis of symmetry to move a little bit on the side of n=1, so that f(1).

an is a quadratic function, -k 2 is the position of the axis of symmetry, and 3 2 is, (1+2) 2, i.e., a2 a1 is guaranteed. A quadratic function with the opening upward, the right half of the branch is incremental.

Proof 1: Pass point C as CF perpendicular to point F

Because ab||cd, angle a = 90°

So the angle d=90°

And because the angle A and D are equal to 90°, the AFCD is rectangular, and AD=CF so CD=AF=1

And because ab=2, bf=1

And because bc=3, cf=2 times the root number 2

So ad=cf=2 times the root number 2

And because the point e is the midpoint, de=ae=root number 2

So the rest of myself should be able to write...

2: Similar. Proof 2: It's about the same as the first step, typing is too slow, cd is better than ce, de is better than eb, the angle is 90 °, just use the corners, generally this kind of question is valid, take a good look at it yourself, I feel like I have done it in the second year of junior high school, hehe.

The first one is denoted as:

The second one is denoted as:

This kind of representation is called descriptive method, which is often used to represent an infinite set, and the common attributes of the elements in the set are described in words, symbols or formulas, etc., and written in curly brackets.

Is this a system of two equations?

If there are two, they are: k (3,4); k∈（4，5）

Classmates, I suggest you ask your classmates will be faster, because there must be great classmates, and they rarely come!

2k-1=6 k=7 2 (off-topic) 2k-1=-6 k=-5 2

3 2-k = 3 2 + 5 2 = 4, and the square roots of 4 are +2 and -2

2x-1=6 gives x= substitution without square root.

x= of 2x-1=-6 is substituted with square root and square root is plus or minus 2

Hello, satisfied, thank you.

Just with him like a tiger in the collegial court.