Answer: A.
Explanation: 4 + -4 = 0 and 3 - 3 = 0
You did the equation a little wrong. It is A^2 + B^2 = 10^2
7/10-1/2=←Write the equation
7/10-5/10=←Make it into a common denominator and subtract
2/10=←Simply if possible
1/5←This is the simplest form