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Three Dimensional Geometry

Question
CBSEENMA12033389

Find the equation of the plane which is parallel to the x-axis and has intercepts 5 and 7 on the y and z-axis, respectively.

Solution
Let the equation of plane be
          straight x over straight a plus straight y over straight b plus straight z over straight c equals 1                                     ...(1)
Here b = 5,    c = 7                                               ...(2)
Since the plane is parallel to x-axis whose direction ratios are 1, 0, 0
∴   normal to the plane must be perpendicular to the x-axis. But the direction ratios of the normal to the plane are 1 over straight a comma space 1 over straight b comma space 1 over straight c.
therefore space space space space 1 over straight a cross times 1 plus space 1 over straight b cross times 0 space plus space 1 over straight c cross times 0 space equals space 0 space space space space space space space rightwards double arrow space space space space space 1 over straight a space equals space 0              ...(3)
From (1) and (2), (3), we have
straight y over 5 plus straight z over 7 space equals space 1 space space space space or space space 7 straight y space plus space 5 straight z space equals space 35
which is required equation of plane.