theorem Th42: :: BKMODEL4:49

for a, b, c being Real
for u, v, w being Element of (TOP-REAL 3) st a <> 0 & (a + b) + c = 0 & ((a * u) + (b * v)) + (c * w) = 0. (TOP-REAL 3) holds
u in Line (v,w)