modulo 13 sqrt(x) + sqrt(x+1) = sqrt(2x+1) /**/ <=> x >= 0 /\ x + 2 sqrt(x) sqrt(x+1) + x+1 = 2x+1 /**/ <=> x >= 0 /\ sqrt(x) sqrt(x+1) = 0 /**/ <=> x >= 0 /\ (x=0 \/ x=-1) /**/ <=> x=0
Which numbers do have a square root modulo 11?
modulo 11 EE b: b^2 = a <=> a=0 \/ a=1 \/ a=3 \/ a=4 \/a=5 \/ a=9