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We will have the same amount of money if I give my brother $5. Instead, if he offers me $25, I'll have twice as much cash as he does.  

 

Well........ if he only offers $25 nothing changes.  

He would have to actually hand over the $25.  

But I think I know what you mean.  

 

Let M stand for My original amount  

Let B stand for Brother's original amount   

 

                                                             (M – 5)  =  (B + 5)   

                                                             (M + 25)  =  (2)(B – 25)  

 

                                                              M – 5  =  B + 5   gives us  M = B + 10    (1)  

 

                                                              M + 25  =  2B – 50                                 (2)  

 

Substitute the value of M from (1)   

into the equation (2)                             B + 10 + 25  =  2B – 50   

 

Combine like terms                                          85  =  B    

 

Brother has 85 dollars before they start swapping moneys.   

 

My amount is 95 dollars   

 

Check answer  

 

If I give my brother 5, then I'll have 90 and so will he, so we have the same.  

If my brother gives me 25, then I'll have 120 and my brother will have 60.  

.

Jul 13, 2023
 #4
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Hi Ron,

 

LOL. I’m familiar with that location. It’s the same place that some of the forum’s homework-mooching students shove the detailed-answer-solutions presented by competent answerers.    

 

Submitted for your education and disapproval, Web2.0calc’s Math Forum, formally one of the repositories of knowledge for the bright and brilliant-minded, and also the drab and undistinguished, dusty-minded dolts who have propensity for falling into uncovered manholes while reading math solutions on their phones; now, a forum cluttered with suppositories waiting for the bone-heads, who set all educational topics back 3000 years as their brain dies decades before death claims the rest of them.

Why suppositories? Because shoving it up their ass is the only way to get the knowledge into them. Of course, as soon as they take a shit they lose that knowledge, but a copy remains on their homework.

Source: https://web2.0calc.com/questions/we-should-really-put-this-site-on-brave-as-a-verified-website#r7

 

One group shoves correct answers in and the other group pulls wrong answers out.

(It’s amazing how many analogues are found in nature and in metaphorical descriptions.)

 

BTW, your post was hidden by the auto-moderator. [I actually saw it happen, but I didn’t have time to deal with it. I also didn’t know if it was you or one of the BS question-spamming or Wrong Answer Trolls, offering more troll bait.] When this happens, you can send a message to Melody or Alan, requesting restoration to normal viewing. Be sure to include the link to your post. 

 

[I long ago figured out how to circumvent the auto-moderator (and the curse filter). If I hadn’t, most of my troll posts would reside in perpetual, invisible obscurity. Though not a troll post per se, my retort and commentary above definitely would not have made it past the auto-moderator. Your post didn’t, and there is nothing untoward about it.  

 

Although I’ve figured out how to circumvent the auto-moderator, I’ve not figured out how to circumvent the human moderators; that requires a much more complex solution.LOL  LOL I suppose, though, in the past seven to nine years, Melody, Alan, and CPhill (when he was in attendance) became use to my peppery and ass-biting commentaries, and maybe even found redeemable social values in some of them. (I’d like to think so, anyway.)

 

Speaking of troll posts, JB, who lives to read my troll posts, sent me an email a few weeks ago saying this troll post, https://web2.0calc.com/questions/turning-point-vs-symmetry#r5, is now the funniest; moving the one I delivered to you,

https://web2.0calc.com/questions/the-cubs-are-playing-the-red-sox-in-the-world-series_1#r2, to a close second.   I’m wondering if JB might switch their superlative positions after the novelty of my recent post wares off. Maybe Yes, Maybe No.]

 

GA !

--. .- 

Jul 13, 2023
 #1
avatar+8 
0

To find the sum of f(1) + f(2) + ... + f(40), we can simplify each term and then calculate the sum.

Let's simplify f(n) for any positive integer n:
f(n) = 4n / (sqrt(2n - 1) + sqrt(2n + 1))

To simplify the expression, we can multiply both the numerator and the denominator by the conjugate of the denominator, which is (sqrt(2n - 1) - sqrt(2n + 1)):

f(n) = (4n / (sqrt(2n - 1) + sqrt(2n + 1))) * ((sqrt(2n - 1) - sqrt(2n + 1)) / (sqrt(2n - 1) - sqrt(2n + 1)))

Simplifying further, we get:

f(n) = (4n * (sqrt(2n - 1) - sqrt(2n + 1))) / ((2n - 1) - (2n + 1))
= (4n * (sqrt(2n - 1) - sqrt(2n + 1))) / (-2)

Now we can calculate the sum of f(1) + f(2) + ... + f(40):

sum = f(1) + f(2) + ... + f(40)
= (41(sqrt(21 - 1) - sqrt(21 + 1)))/(-2) + (42(sqrt(22 - 1) - sqrt(22 + 1)))/(-2) + ... + (440(sqrt(240 - 1) - sqrt(240 + 1)))/(-2)
= -2 * (1*(sqrt(21 - 1) - sqrt(21 + 1)) + 2*(sqrt(22 - 1) - sqrt(22 + 1)) + ... + 40*(sqrt(240 - 1) - sqrt(240 + 1)))

Now we can simplify each term in the parentheses and calculate the sum:

sum = -2 * (1*(sqrt(21 - 1) - sqrt(21 + 1)) + 2*(sqrt(22 - 1) - sqrt(22 + 1)) + ... + 40*(sqrt(240 - 1) - sqrt(240 + 1)))
= -2 * (1*(sqrt(1) - sqrt(3)) + 2*(sqrt(3) - sqrt(5)) + ... + 40*(sqrt(79) - sqrt(81)))

We can see that the terms inside the parentheses form a telescoping series, where the square root terms cancel each other out. The only terms that remain are the first and the last:                    YourTexasBenefits Login

sum = -2 * (sqrt(1) - sqrt(3) + sqrt(3) - sqrt(5) + ... + sqrt(79) - sqrt(81))
= -2 * (sqrt(1) - sqrt(81))
= -2 * (1 - 9)
= -2 * (-8)
= 16

Therefore, the sum of f(1) + f(2) + ... + f(40) is 16.

Jul 13, 2023
Jul 12, 2023

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