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Question : 116 of 130
Marks:
+1,
-0
Solution:
Two planes are coplanar if
|| x2−x1 | y2−y1 | z2−z1 |
| l1 | m1 | n1 |
| l2 | m2 | n2 |
|=0 ||=0Applying
C2→C2+C1,C3→C3+C1||=0‌⇒1[2+2k−(k+2)(1−k)]=0‌⇒2+2k−(−k2−k+2)=0‌k2+3k=0⇒k(k+3)=0
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