Question

Find the value of alpha so that A vector =2icap-jcap+kcap,B vector=ICAP+2jcap-3kcap and C vector=3icap+alphajcap+5kcap are coplanar.​

Answer 1

Explanation:

Three vectors, a, b, c are coplanar if [abc]=0

or

∣

∣

∣

∣

∣

∣

∣

∣

2

1

3

−1

2

λ

1

−3

5

∣

∣

∣

∣

∣

∣

∣

∣

=0

or 2(10+3λ)+1(5+9)+1(λ−6)=0 ( expanding along first row.)

or 7λ+28=0∴λ=−4