>>11582276For example, say we're looking at the n = 2 case.
Maybe P_1 = a + bx and P_2 = c + dx + ex^2 + fx^3, with b and f nonzero.
We want to show that, if sP_1 + tP_2 = 0, then s = t = 0.
Well, we expand:
sa + sbx + tc + tdx + tex^2 + tfx^3 = 0
then tf = 0, but f is nonzero so t = 0.
But now we have sP_1 = 0. So s = 0.
