1.

The plane through the intersection of the planes `x+y+z=1` and `2x+3y-z+4=0` and parallel to Y-axis also passes through the pointA. (3, 3, -1)B. (-3, 1, 1)C. (3, 2, 1)D. (-3, 0, -1)

Answer» Correct Answer - C
Equation of poane through the intersection of two planes `P_(1)` and `P_(2)` is given by `P_(1)+lambdaP_(2)=0`
The plane through the intersection of the planes `x+y+z-1=0` and `2x+3y-z+4=0` is given by
`(x+y+z-1)+lambda(2x+3y-z+4)=0,`
where `lambdainR`
`implies(1+2lambda)x+(1+3lambda)y+(1-lambda)z+(4lambda-1)=0,`
where `lambdainR" "...(i)`
Since, this plane is parallel to Y-axis, therefore its normal is perpendicular to Y-axis, therefore its normal is perpendicular to Y-axis.
`implies" "{(1+2lambda)hati+(1+3lambda)hatj+(1-lambda)hatk}.hatj=0`
`implies" "1+3lambda=0implies" "lambda=-(1)/(3)`
Now, required equation of plane is
`(1-(2)/(3))x+(1-(3)/(3))y+(1+(1)/(3))z+(-(4)/(3)-1)=0`
[substituting `lambda=(-1)/(3)` in Eq. (i)]
`impliesx+4z-7=0`
Here, only (3, 2, 1) satisfy the above equation.


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