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Matrices

Question
CBSEENMA12035644

Show that the four points A(4,5,1), B(0,-1,-1), C(3,9,4) and D(-4,4,4)
are coplanar.

Solution

Given  four points A(4,5,1), B(0,-1,-1), C(3,9,4) and D(-4,4,4).
therefore,
AB with rightwards arrow on top space equals space left parenthesis negative 4 i with hat on top minus 6 j with hat on top minus 2 k with hat on top right parenthesis

AC with rightwards arrow on top space equals space left parenthesis negative i with hat on top plus 4 j with hat on top plus 3 k with hat on top right parenthesis

AD with rightwards arrow on top space equals space left parenthesis negative 8 i with hat on top plus j with hat on top plus 3 k with hat on top right parenthesis

therefore space space vertical line AB with rightwards arrow on top space space AC with rightwards arrow on top space space AD with rightwards arrow on top vertical line space equals space open vertical bar table row cell negative 4 end cell cell negative 6 end cell cell negative 2 end cell row cell negative 1 end cell 4 3 row cell negative 8 end cell 1 3 end table close vertical bar

equals space minus 4 left parenthesis 12 space plus space 3 right parenthesis space plus space 6 left parenthesis negative 3 space plus space 24 right parenthesis space minus space 2 left parenthesis 1 space plus space 32 right parenthesis

equals space minus 60 space plus space 126 space minus space 66

equals 0
Hence comma space Four space points space straight A comma space straight B comma space straight C comma straight D space are space coplanar.