Find the value of `lambda` so that the three vectors are co-planar. `hati+2hatj+3hatk, 4hati+hatj+lambdahatk` and `lambdahati-4hatj+hatk`

Explanation

Let `veca = hati+2hatj+3hatk`
`vecb = 4hati+hatj+lambdahatk`
`vecc = lambdahati-4hatj+hatk`
If the given vectors are coplanar, then `vecaxxvecb.vecc = 0`

`2lambda^2+11lambda-10lambda-55 = 0`
`implies lambda(2lambda+11)-5(2lambda+11) = 0`
`implies(lambda-5)(2lambda+11) = 0`
`implies(lambda-5)(2lambda+11) = 0`
`implies lambda = 5` or -11/2