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Mathematics Question on Vectors

If a→=i^+λj^−2k^,b→=2i^−3j^+5k^ and a→⋅b→=−20\overrightarrow{a}=\hat{i}+\lambda\hat{j}-2\hat{k}, \overrightarrow{b}=2\hat{i}-3\hat{j}+5\hat{k}\ and\ \overrightarrow{a}\cdot\overrightarrow{b}=-20, then the value of λ\lambda is equal to

A

2

B

-2

C

-4

D

4

E

5

Answer

4

Explanation

Solution

The correct option is (D): 4