Not an easy answer w/ the limited information provided. First, I'm assuming that you are using the 'native' photo app on the iPad; if so, what version iOS are you running on the iPad? The 'photo app' for the iPad was updated w/ release of the newest iOS, v. 5x - just a starter.
Second, if using the most recent version of the 'native' photo app, is this photo located in the 'camera roll' or elsewhere - may also help to know how the photo was put onto the iPad, i.e. from the camera, from a sync, or other method?
Please respond and more specific advice can be given - good luck!
Yes as Giradman said we do need to know more here.
The IPad Forum is a community of members from all walks of life and from all over the world coming together to share our experiences and to help each other learn about this wonderful piece of technology the Ipad. There is a wealth of information already here in the many threads we have so doing some searches will answer most of the questions you have. If then you cannot find the answer you are seeking then by all means post your question. There are many friendly and informed members here only too willing to help you.
For remove only one photo, clic on it, and in the top right corner is the recycl bin button...
For remove 2 or more... Seeing the photos in thumbnails clic in the top right corner, in the arrow and start to clic on each photo and un the top left corner is "Delete" button...