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    				| 1. | It is given that the vectors`vec(a)=(2hat(i)-2hat(k)), vec(b)=hat(i)+(lambda +1)hat(j) and vec(c)=(4hat(j)+2hat(k))` are coplanar. Then, the value of `lambda` isA. `(1)/(2)`B. `(1)/(3)`C. 2D. 1 | 
| Answer» Correct Answer - D Since `vec(a),vec(b),vec(c)` are coplanar, we must have `[vec(a)vec(b)vec(c)]=0` Now, `[vec(a)vec(b)vec(c)]=|(2,0,-2),(1,lambda+1,0),(0,4,2)|` `=2(2lambda+2-0)-2(4-0)` `=4lambda+4-8=4lambda-4` `:. [vec(a)vec(b)vec(c)]=0 hArr 4lambda-4=0hArr 4 lambda=4 hArr lambda=1`. | |