theorem Th9: :: CQC_THE1:13

for Al being QC-alphabet
for X being Subset of (CQC-WFF Al)
for p, q being Element of CQC-WFF Al
for x being bound_QC-variable of Al st p => q in Cn X & not x in still_not-bound_in p holds
p => (All (x,q)) in Cn X