JEE Mains · Maths · STD 12 - 10. vector algebra
Let \(\overrightarrow{ a }=\hat{ i }+2 \hat{ j }-3 \hat{ k }\) and \(\overrightarrow{ b }=2 \hat{ i }-3 \hat{ j }+5 \hat{ k }\). If \(\overrightarrow{ r } \times \overrightarrow{ a }=\overrightarrow{ b } \times \overrightarrow{ r }, \overrightarrow{ r } \cdot(\alpha \hat{ i }+2 \hat{ j }+\hat{ k })=3\) and \(\vec{r} (2 \hat{ i }+5 \hat{ j }-\alpha \hat{ k })=-1, \alpha \in R ,\) then the value of \(\alpha+|\overrightarrow{ r }|^{2}\) is equal to :
- A \(9\)
- B \(15\)
- C \(13\)
- D \(11\)
Answer & Solution
Correct Answer
(B) \(15\)
Step-by-step Solution
Detailed explanation
\(\overrightarrow{ r } \times \overrightarrow{ a }=\overrightarrow{ b } \times \overrightarrow{ r } \Rightarrow \overrightarrow{ r } \times(\overrightarrow{ a }+\overrightarrow{ b })=0\)…
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