hey guys! please help me with this?!!!k

A(1,3)

B(2,6)

those are the points on the graph and they want me to fine the distancebetween points A and B... welll i like worked out the problem step by step and i keep getting i differnet answer that is in the book!!! i need som serious help! could you please!!!

i keep getting 10 for an answer and the answer says it is 30. and i can not see where i keep making the mistake can you please help me. THANK YOU SOO MUCH!

Minthie Jo