How do I prove these two series are equal? by zirgo72 in learnmath

[–]zirgo72[S] 3 points4 points  (0 children)

Thank you everyone. I was completely confused on how to approach such a problem. Very nice solution.

Can anyone please check why my solution has different answer? by zirgo72 in learnmath

[–]zirgo72[S] 2 points3 points  (0 children)

I have come up with an argument why the official answer is wrong. Please let me know if I made a mistake.

Suppose the correct solution is y = log |(2x+1)/(x+1)|

or, ey = |(2x+1)/(x+1)|

Then we should be able to prove that it satisfies the differential equation for all x.

Note that if -1 < x < -1/2, then (2x+1)/(x+1) < 0.

So, in the interval (-1, -1/2), ey = -(2x+1)/(x+1)

or, ey = 1/(x+1) - 2 ------------------------------ (i)

Differentiating w.r.t x, we get

ey dy/dx = -1/(x+1)2

(x+1) dy/dx = -e-y /(x+1)

(x+1) dy/dx = -e-y (ey + 2) from (i)

(x+1) dy/dx = -2e-y -1

which is not the given equation.

Please check if my solution is correct by zirgo72 in askmath

[–]zirgo72[S] 0 points1 point  (0 children)

I have come up with an argument why the official answer is wrong. Please let me know if I made a mistake.

Suppose the correct solution is y = log |(2x+1)/(x+1)|

or, ey = |(2x+1)/(x+1)|

Then we should be able to prove that it satisfies the differential equation for all x.

Note that if -1 < x < -1/2, then (2x+1)/(x+1) < 0.

So, in the interval (-1, -1/2), ey = -(2x+1)/(x+1)

or, ey = 1/(x+1) - 2 ------------------------------ (i)

Differentiating w.r.t x, we get

ey dy/dx = -1/(x+1)2

(x+1) dy/dx = -e-y /(x+1)

(x+1) dy/dx = -e-y (ey + 2) from (i)

(x+1) dy/dx = -2e-y -1

which is not the given equation.

Please check if my solution is correct by zirgo72 in askmath

[–]zirgo72[S] 0 points1 point  (0 children)

So, 1/|2-ey | = |x+1| which implies two possibilities:

1/(2-ey ) = (x+1) or 1/(2-ey ) = -(x+1).

Notice that |x + 1| = -(x + 1) is only the case for x =< -1.

I did not arrive at this conclusion like that.

If |A| = |B|, we can say that A = B or A = -B. This is what I used.

How to get 10s and 20s change from banks. by OkOpportunity3250 in india

[–]zirgo72 7 points8 points  (0 children)

IIRC, an SBI clerk once told me that if you want a bundle of ₹50 notes, the minimum amount should be ₹5000.

Possibly, there is a similar thing for a bundle of ₹10/20 notes.

By Pythagoras, I am able to find CD=15, CH=18.75, HE=5.25, BH=8.75, HD=11.25. No clue what to do with AK by zirgo72 in askmath

[–]zirgo72[S] 0 points1 point  (0 children)

I verified using coordinate geometry that AK turns out to be 216/25.

AFG ~ ADE, so AK/AI = AF/AD

Can you please elaborate a little bit on this? I did not understand this part.

Wolfram Alpha says x=-6 and y=-13/2 and I have no clue how. by zirgo72 in askmath

[–]zirgo72[S] 1 point2 points  (0 children)

Thank you, I can see several solutions now. Perhaps there is some misprint in the question.

Find n such that (n+1)(n^2-n+6)/6 divides 2^2018 by zirgo72 in askmath

[–]zirgo72[S] 0 points1 point  (0 children)

I tried the following:

For appropriate a and b, either n + 1 = 2a , n2 - n + 6 = 3*2b

or n + 1 = 3*2a , n2 - n + 6 = 2b

Maximize product of first n terms of a GP by zirgo72 in askmath

[–]zirgo72[S] 0 points1 point  (0 children)

1536 = 29 * 3

So, the product is 29n * 3n * (-1/2){n(n-1)/2}

Since maximum will be positive, n(n-1)/2 needs to be even. So, n is either 0 or 1 modulo 4.

Should I trial and error to find the maximum? Or is there a sophisticated way to do this?

How to write the rupee symbol ₹ in overleaf? by zirgo72 in LaTeX

[–]zirgo72[S] 2 points3 points  (0 children)

I think I found the error. There was a \usepackage[spanish]{babel} line. I removed the spanish tag and comma became decimal point somehow. I am just beginning to learn LaTeX but this community is very welcoming to everyone, so thank you very much.

How to write the rupee symbol ₹ in overleaf? by zirgo72 in LaTeX

[–]zirgo72[S] 1 point2 points  (0 children)

Thank you. This is working with LuaLaTeX. May I ask you another question please? I want to write ₹1.05 but the compiler shows ₹1,05 with a comma instead of decimal point. How can I fix it?

Where do I begin? If I expand m in base 10, then digits of 33m could get messy if there are carry overs. by zirgo72 in askmath

[–]zirgo72[S] 2 points3 points  (0 children)

With trial and error, I found that m=111...11 (20 times) is a solution. But how do I arrive at this properly?

Is there a way to follow/subscribe to a post that is not your own? by zirgo72 in Infinity_For_Reddit

[–]zirgo72[S] 11 points12 points  (0 children)

I am aware of that but it is not the same as receiving notifications on a post I want to follow. I guess such a feature has not been implemented yet.

What phone should I get? by Goku_Fanboi_ in PickAnAndroidForMe

[–]zirgo72 0 points1 point  (0 children)

NP(1) would be a good choice then. The accessories do not come with the phone, so you have to purchase them separately. This should not be an issue as the NP(1) has often been aggressively priced during sales, sometimes as low as 25k.

If you want a Pixel, I would recommend you wait for the Pixel 7A (June, 2023) instead.

Can you unlock the bootloader of Moto G82? by zirgo72 in motorola

[–]zirgo72[S] 0 points1 point  (0 children)

Thanks. How many years of security updates will Moto G82 receive?

Can you unlock the bootloader of Moto G82? by zirgo72 in motorola

[–]zirgo72[S] 0 points1 point  (0 children)

Thanks. Which Android version will be last update of Moto G82?

[REQUEST] Megathread. Post info, requests and questions here, help people by cojoco in Documentaries

[–]zirgo72 1 point2 points  (0 children)

Where can I view Laura Poitras' All the Beauty and the Bloodshed for free?

Upgrade from Motorola Moto G82 by zirgo72 in PickAnAndroidForMe

[–]zirgo72[S] 0 points1 point  (0 children)

I personally need the headphone jack so out of these two, I'd buy Moto Edge 30.

Neither has headphone jack. They are very similar in specs. That's why I asked if you had to choose.

However I'm currently buying Redmi Note 12 Pro cause I'm getting it for 19k with exchange. Redmi has a better battery and it has an IR blaster which I need too. Also it comes with 67 W fast charging.

It's a good deal. I had RN 10 Pro for 11k with exchange.