ReCaptchas have this built-in functionality where they feel that they're helping to digitize books or some such, so they always show two words... a known one and some random text snippet. The thing is, they don't even know what the snippet says. All they use to verify what you type is the "known" half of the puzzle. You can literally type whatever the heck you want for the first or second word (whichever is the random snippet... you can usually tell by the font now that you know what they're doing).
Of course, by typing in junk you're not really helping their project... but when they show you math symbols and images and crap they really can't blame you.
Now, the thing about recaptchas is that it's hard to read the other part too.... looks like you got some r's there, and maybe an n or an m smooshed in there too...

I generally fail more recaptchas than I get right, and that's knowing that only one of the words has to be right... The other one you got there is lambda sub t of P, but it doesn't matter, type a single letter or whatever bit of profanity you like...

Edit: I shoulda read the first page, where PBJ said exactly what I just said. Also interesting that you guys said it didn't work. I've done it lots of times. Of course like I said, sometimes the one they're really trying to test you on is so illegible and run together that you can't tell what it really is. There are several forms of captcha though, and I believe this only applies to recaptcha. They're the ones working on that project. As far as why it sometimes gets completely random crap, I assume that's just a byproduct of the code they use to parse things out. I'm sure they're just plugging scans into software and it's supposed to parse it automatically for them. When there's math symbols and images their algorithm likely fails.
Here, you can try them direct from the source as many times as you like. I just tried a few... typed complete garbage for the words that were more clearly scans. Told me I was correct every time.
https://www.google.com/recaptcha/learnmoreAh, just saw that PBJ said you only have to type "the more legible word" correctly. That's not quite correct. You have to type the wavy/distorted one correctly. Sometimes the "decoy" portion is very legible. There will be one weird wavy distorted word and one word that looks like a scanned word (or symbol, or image, or random garbage). You type the distorted one correctly.... if you can make it out.