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 The values of k for which the points A(1,0,3),B(1,3,4),C(1,2,1) and D(k.2,5) are coplanar, are 

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detailed solution

Correct option is D

Let a=(1,0,3),b=(−1,3,4),c=(1,2,1) and d=(k,2,5) . Since A,B,C and D are coplanar, we have [dbc]+[dca]+[dab]=[abc]⇒k−11   2  3  2  541+k  1  1  220  5 1 3+k25103-134=1  −11   0    3    2    3    4     1⇒   −5k−15+6k−14−9k+1= −20⇒   −8k−28=−20           ⇒      k=−1


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