let i be Nat; :: thesis: for R1, R2 being Element of i -tuples_on REAL holds R1 - (- R2) = R1 + R2
let R1, R2 be Element of i -tuples_on REAL ; :: thesis: R1 - (- R2) = R1 + R2
thus R1 - (- R2) = R1 + (- (- R2)) by FINSEQOP:89
.= R1 + R2 ; :: thesis: verum