taking lambda as L and Miu as M
- Proof
let L != 0
if so
a = -(M/L)b <---- this is in the form of a = kb
this format means a is parallel to b (a // b)
But by definition a and b are non prallel, therefore this is impossible
So L has to be 0
if L = 0
La + Mb = 0
0*a + Mb = 0
Mb = 0
This means either (M = 0) or (b = 0)
But by definition a and b are non zero, therefore (b = 0) is impossible
So M has to be 0
So now let, L = 0 and M = 0
La + Mb = 0
0 + 0 = 0
Therefor La + Mb = 0 only if (L = 0) and (M = 0)