The proxy worked, you just got a Captcha challenge. It pulled up Google just fine. If the proxy were dead you would have gotten a 403, 404 or 5xx errors.
Google gets destroyed by public proxies all day long, so being challenged by a captcha is pretty much to be expected. Look at your HTTP headers though, you're getting HTTP 200s which means successful, you'll just need to have a Captcha solution in place if you'll be scraping with public proxies.
The rules are: private proxies for scraping, public proxies for submitting. This is the reason why. Scraping with public proxies sucks and it's never free because you have to pay for Captchas or miss out on data.
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Google gets destroyed by public proxies all day long, so being challenged by a captcha is pretty much to be expected. Look at your HTTP headers though, you're getting HTTP 200s which means successful, you'll just need to have a Captcha solution in place if you'll be scraping with public proxies.
The rules are: private proxies for scraping, public proxies for submitting. This is the reason why. Scraping with public proxies sucks and it's never free because you have to pay for Captchas or miss out on data.