The arithmetic sequence is 9.19.29.39. Then 409 is the () th item

The arithmetic sequence is 9.19.29.39. Then 409 is the () th item

(409-9)/(19-9)+1=41

Ln [x + (x ^ 2 + 1) ^ (1 / 2)] is expanded into a power series of X

The derivative is 1 / √ (1 + x ^ 2) = (1 + x ^ 2) ^ (- 1 / 2) = 1 + (- 1 / 2) * x ^ 2 +... + [(- 1) ^ n * 1 / 2 * 3 / 2 *... * (2n-1) / 2] / N! * x ^ (2n) +... = 1 + ∑ [(- 1) ^ n * (2n-1)! / (2n)!] * x ^ (2n), n from 1 to ∞
Re integration, LN [x + √ (x ^ 2 + 1)] = x + ∑ [(- 1) ^ n * (2n-1)! / ((2n)! × (2n + 1))] * x ^ (2n + 1), n from 1 to ∞. The convergence domain is [- 1,1]

What is the sum of square minus 2a of a plus 2 and four minus 8 of a?

(a + 2) / (a-2a) + 8 / (4-A) = (a + 2) / [a (A-2)] - 8 / [(A-2) (a + 2)] = [(a + 2) - 8A] / [a (A-2) (a + 2)] = (a-4a + 4) / [a (A-2) (a + 2)] = (A-2) / [a (A-2) (a + 2)]; denominator = (A-2) / [a (a + 2)]

It is known that m ∈ R is the two roots of the equation x2-ax-2 = 0 for P: X1 and X2, the inequality | m-5 | ≤ | x1-x2 | holds for any real number a ∈ [1,2]; Q: the function f (x) = 3x2 + 2mx + m + 43 has two different zeros. The range of real number m which makes "P and Q" true is obtained

In this paper, we set up the following problem: 1 + x2 = a, x 1 = 2, x 2 = -2, \124\\\\\\124\\\\\\124\\x1-x2 | = (x1 + x2) 2 {(x1 + x2 + 2 + 4x2 + 4x2 + 2 + 2 + 2 + m + m + 43 = 0, we get the discriminant of F (x) f (x) = 3x2 + 2x2 + 2x2 + 2x2 + 2x2 + 2x2 + 2x2 + 2x2 + 2 + 2x2 + 2 + 2 + 2 + m + m + m + 43 + 43 = 4m2 + 2 + 12 (M + 4) to sum up, "P and Q" should be true If P is true and Q is true, i.e. 2 ≤ m ≤ 8m ＜ 1 or M > 4, the value range of real number m is (4,8]

What is the quotient of 8 / 9 divided by the sum of the largest digit and its reciprocal

According to the meaning of the question: 8 / 9 △ 9 + 1 / 9 = 8 / 9 △ 82 / 9 = 8 / 82 = 4 / 41

If a polynomial squared is a monomial and contains x ^ 2 + 25, then the polynomial is____
If we add a monomial to x + 25 and make it a complete square with X, then the monomial is_____ If we add a monomial to x + 25 and make it a square, then the monomial is_____ ；

If we add a monomial to x ^ 2 + 25 and make it a complete square with X, then the monomial is_
±10x,x^4/100 ____ ；

1. If the difference between two numbers is 3, if the larger number is x, then the functional expression of their product y and X is,
It has the most () value, that is, when x=____ When, y=_____
2. The parabola y = x2 + kx-2k passes through a fixed point to find the coordinates of the fixed point

1. If the two numbers are: X, x-3, then
y=x（x-3）；
There is a minimum value;
y=x（x-3）=（x-3/2）^2-9/4
When x = 3 / 2, y = - 9 / 4
2、y=x^2+kx-2k=x^2+k(x-2)
When x = 2, y = 4, the fixed point is: (2,4)

For the equation (M + n) x2 + Mn2 - (m-n) x = 0 (M + n ≠ 0) of X, if the sum and difference of the coefficients of quadratic term and primary term are 12 and 2, then the constant term is ()
A. 18B. 12C. 116D. 14

According to the meaning of the title: (M + n) − (m − n) = 12 (M + n) + (m − n) = 2, the solution is: M = 1n = 14, so the constant term is: Mn2 = 14 × 12 = 18

Subtract a number from the sum of 3 / 4 and 1 / 3, and the difference is 7 / 12

3/4+1/3-7/12
=9/12+4/12-7/12
=(9+4-7)/12
=6/12
=1/2

Let a be an invertible matrix, then the matrix with the same eigenvalue as a is ()
A. At (t in superscript position) B.a2 (2 in superscript position)
C. A-1 (- 1 in superscript position) D.A*
Thank you for your reply

Choose a
Because | xe-at | = | (xe-a) t | = | xe-a|