Question

The value of 'm' for which the straight line

3x –2y + z + 3 = 0 = 4x – 3y + 4z + 1 is parallel to the plane 2x – y + mz – 2 = 0 is –

• A. –2
• B. 8
• C. – 18
• D. 11

Answer 1

Answer: (A)

–2

Answer 2

a, b, c be dr's of line

3x – 2y + z + 3 = 0 = 4x –3y + 4z + 1

so 3a – 2b + c = 0 and 4a – 3b + 4c = 0

so a : b : c = 5 : 8 : 1

dr's of plane 2x – y + mz – 2 = 0 is 2, –1, m

for line to be parallel to plane i.e. line is perpendicular to the normal to the plane so

5.2 + 8(–1) + 1. m = 0

̃ m = –2