Math Is Fun Forum

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Hi Lana2001,

What happens when you substitute r = b into your equation?

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Hi Pema,

What do you get when you add A and B together?

What kind of matrix is it, and what do we know about powers of these matrices?

and a sequence

You need about 25 terms in the series above to get all the primes less than 100, for example.

Hi Zeeshan 01,

Is there something missing from your post?

Welcome!

Hi all,

This thread is an exact copy of this thread. (As you can see, the poster above simply copied the plaintext from that thread, including the signature. Some of the other links the post contained were also removed, probably because the forum doesn't let you post too many links if you're a new user.) Having googled the topic starter's username, they appear to be a run-of-the-mill bot, registering on multiple forums within the last couple of days and creating one single post, taken from somewhere else on the forum it posted on. This is a common theme for spammers or bots who want to spread their links inconspicuously.

For example, the poster most likely used *that* post because it was created five years ago, at a time which most of us probably wouldn't remember. It therefore becomes a suitable candidate for hiding a link somewhere in, which can attract spammers, or even worse, if accidentally clicked, could cause harm to an unsuspecting victim. No hyperlinks were disguised in this post, thankfully. Sometimes bots also make multiple posts like this before their account gets link-posting privileges, at which point, they can post as much spam as they like until someone stops them. Both of these things happen surprisingly often, and can be quite messy to clean up! Spammers will try all sorts of tricks to get their posts out! One annoying fellow earlier today decided to mix Arabic letters in with the English letters in their username so I could not highlight it as usual in order to ban them.

I won't delete the post or ban them yet (on the slight off-chance they might not have bad intentions), but will keep an eye on them. I think it serves as a useful demonstration of the kinds of threats that our forum can potentially be vulnerable to.

Welcome, Xavier!

Hi,

You might find this link useful: https://www.mathsisfun.com/algebra/poly … lying.html

Hi Russia,

Have you considered registering an account with us? You can do this by clicking here.

The old price of the coat is $20, and the new price is $15. That means the price has reduced by $5 (since 20 - 15 = 5). So now you just need to find out how much percent $5 represents as a fraction of the old price. This is:

Please let us know if you need any further help!

No worries -- let's look at part (a) first.

If we 'multiply out' the left-hand side, we get:

Now, we can add two vectors just by adding the matching components, so that:

which is exactly the same as solving the pair of simultaneous equations:

Let me know if this makes sense -- happy to explain anything further if you need more help.