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Integrals

Question
CBSEENMA12036131

If the image of the point P(1, –2, 3) in the plane, 2x + 3y – 4z + 22 = 0 measured parallel to line, x/1 = y/4= z/5 is Q, then PQ is equal to

  • 6 square root of 7
  • 3 square root of 5
  • 2 square root of 42
  • square root of 42

Solution

C.

2 square root of 42
Line space PQ space semicolon space fraction numerator straight x minus 1 over denominator 1 end fraction space equals fraction numerator straight y plus 2 over denominator 4 end fraction space equals space fraction numerator straight z minus 3 over denominator 5 end fraction
Let space straight F space left parenthesis straight lambda space plus 1 comma space 4 straight lambda minus 2 comma space 5 straight lambda plus 3 right parenthesis
straight F space lies space on space the space plane
2 left parenthesis straight lambda plus 1 right parenthesis space plus space 3 left parenthesis 4 straight lambda minus 2 right parenthesis minus 4 left parenthesis 5 straight lambda plus 3 right parenthesis space plus space 22 space equals space 0
rightwards double arrow space minus 6 straight lambda space plus space 6 space equals space 0
rightwards double arrow space straight lambda space equals 1
straight F space left parenthesis 2 comma 2 comma 8 right parenthesis
PQ space equals space 2 PF space equals space 2 square root of 42

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