Combination of r Things from n Things When All Are Not Different
If a⃗=6 î+8 k...
Question
If →a=6^i+8^k,→b=10^i,4→c=→a+→b and 2→d=→a−→b then which of the following statement is/are correct?
A
|→c+p→d|=|→c−p→d|∀p∈R
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B
→c is perpendicular to →d
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C
→c+→d is perpendicular to →c−→d
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D
|→a|=|→b|=√5|→c|=√5|→d|
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Solution
The correct options are A|→c+p→d|=|→c−p→d|∀p∈R B→c is perpendicular to →d C→c+→d is perpendicular to →c−→d D|→a|=|→b|=√5|→c|=√5|→d| →c=4^i+2^k →d=−2^i+4^k →c⋅→d=(4^i+2^k)⋅(−2^i+4^k)=0
|→c+p→d|2=|→c|2+p2|→d|2+2p→c⋅→d⇒|→c+p→d|=√|→c|2+p2|→d|2 Similarly, |→c−p→d|=√|→c|2+p2|→d|2 So, |→c+p→d|=|→c−p→d|