Let →r=→a+λ→l and →r=→b=μ→m be two lines in space where →a=5^i+^j+2^k,→b=^i+7^j+8^k,→l=−4^i+^j−^kand→m=2^i−5^j−7^k then the p.v. of a point which lies on both of these lines, is
A
^i+2^j+^k
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B
2^i+^j+^k
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C
^i+^j+2^k
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D
non existent as the lines are skew
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Solution
The correct option is A^i+2^j+^k
→r1=→a+λ^i
→r1=(5^i+^j+2^k)+λ(−4^i+^j−^k)
→r1=(5−4λ)^i+(1+λ)^j+(2−λ)^k
→r2=b+μ→m=(^i+7^j+8^k)+μ(2^i−5^j−7^k)
→r2=(1+2μ)^i+(7−5μ)^j+(8−7μ)^k
Given →r1 and →r2 intersect at a part
∴(5−4λ)=(1+2μ)...(1) and (1+λ)=(7−5μ)...(2) and (2−λ)=(8−7μ)...(3)