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Complete the logical proof for the following argument. x(P(x)Q(x))x(R(x)P(x))x(R(x)Q(x)) Let the domain be the set of all positive integers: {1,2,3,}. Are the following expressions true or false? 1. x(x+1=0) 2. xy(x+y=y+x) 3. x(x2x>0) 4. xy((x2=y2)(x=y)) 5. xy(x2=y) 6. xy(x=y)(xy=1)