It is known that the center of the ellipse is O, the major axis and the minor axis are 2a and 2b respectively (a > b > 0), A. B are two points on the ellipse, and OA ⊥ ob, Verification: [1 / (OA Square)] + [1 / (OB) square] is the fixed value

It is known that the center of the ellipse is O, the major axis and the minor axis are 2a and 2b respectively (a > b > 0), A. B are two points on the ellipse, and OA ⊥ ob, Verification: [1 / (OA Square)] + [1 / (OB) square] is the fixed value

4X plus 9 equals x plus 54?
 
1.2x+1+1/(3x+5)≥x-3+1/(3x+5) 2.(x2-5x+6)/(x2-x-2)
. X & gt; = - 4 and X unequal - 5 / 3
X & lt; - 5 or X & gt; - 1 and not equal to 2
X & gt; = (root 17-3) / 2 or X & lt; = (root 17 + 3) / 2
The title is wrong
X & lt; = - 5 or - 1 & lt; = x & lt; = 2 or X & gt; = 3
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A1 = 1, a (n + 1) = an + 2 / an
Let an = tanbn, BN = arctanan. B1 = arctana1 = arctan1 = π / 4, a (n + 1) = an + 2 / an, tanb (n + 1) = tanbn + 2 / tanbnsinb (n + 1) / CoSb (n + 1) = sinbn / cosbn + 2cosbn / sinbn = [1 + (cosbn) ^ 2] / (sinbncosbn) = [1 + (1 + cos2bn) / 2] / (sinbncosbn) = (3 + cos2bn)
What is 4x plus 9 (x + 2) equal to 213
4X + 9 (x + 2) = 213 4x + 9x + 18 = 213, then x = 15
1/(x2+3x+2)+1/(x2+5x+6)+1/(x2+7x+12)=1/(x+4)
solve equations
1/(x²+3x+2)=[(x+2)-(x+1)]/(x+1)(x+2)=1/(x+1) - 1/(x+2)
In the same way
1/(x²+5x+6)=1/(x+2) - 1/(x+3)
1/(x²+7x+12)=1/(x+3) - 1/(x+4)
So the equation becomes 1 / (x + 1) - 1 / (x + 4) = 1 / (x + 4)
The solution is x = 2
Senior two math problems: sequence 1 / Z, 2 / 4, 3 / 8 ,n/2^n,… The general term formula of
The general formula is n / 2 ^ n
Let the sum of the first n terms of the sequence be Sn = 2 - (n + 2) / (2 ^ n)
Interesting. What do you want to ask?
an=n/2^n
I gave it directly in the title
An = n / 2 ^ n at a glance
If you want to sum, you need to subtract by dislocation
The answer is Sn = 2 - (n + 0.5) / 2 ^ n
an=n/2^n
4x-3 times 9 equals 29
4x-3 times 9 equals 29. You don't write clearly. There are two possibilities
The first one is the first one
36x-27=29
36x=56
x=9/14
Second:
4x-27=29
4x=56
x=14
（4x-3)*9=29
4x-3=29/9
4x=29/9+3
x=(29/9+3)/4
9*(4X-3)=29
4x-3 times 9 equals 29
36x-27=29
36X=56
X=9/14
（4X-3）X9=29
36X-27=29
36X=56
X=9/14
How to factorize x2 + 7xy-18y2-5x + 43y-24
Set the factorization form as (AX + by + C) (DX + ey + F) x ^ 2, the coefficient of a = D = 1, the coefficient of XY term 7 = B + D, the coefficient of Y ^ 2-18 = BD, B = 9, d = - 2, and so on. C = - 8, f = 3, finally get x ^ 2 + 7xy-18y ^ 2-5x + 43y-24 = (x + 9y-8) (x-2y + 3) = = = or x ^ 2 + 7xy-18y ^ 2-5x + 4
X2+7xy-18y2-5x+43y-24
=(x-2y)(x+9y)-5x+43y-24
=(x-2y+3)(x+9y-8)
Multiplication of two crosses
x -2y
x 9y
x-2y 3
x+9y -8
Multiplication by cross
x +9y -8
X X
x -2y +3
Namely
Original formula = (x + 9y-8) (x-2y + 3)
General term formula of sequence
1,2 / 3,1 / 2,2 / 5,1 / 3 general term formula~
N belongs to n * -- forgot to give it
2/2,2/3,2/4,2/5,2/6.
So the general formula is 2 / N + 1, n > = 1
2/(n+1)
Let the sequence be SN
Then 1) when n = 2K is even, Sn = 2 / 2K + 1, k = 0,1,2,3
2) When n = 2K + 1 Sn = 1 / 2K + 1 K = 0,1,2,3
2/(n+1)
Everyone knows the answer. It depends on who answers well. I'm late