Question

If a vector $(2\widehat{i} + 3\widehat{j} + 8\widehat{k})$ is perpendicular to the vector $- 4\widehat{i} + 4\widehat{j} + \alpha\widehat{k}$, then the value of a is:

• A. (a) –1
• A. (b) $\frac{1}{2}$
• A. (c) $\frac{- 1}{2}$
• A. (d) 1

Answer 1

(c)

$\overset{\rightarrow}{a}.\overset{\rightarrow}{b}$ = 0 if $\overset{\rightarrow}{a}\bot\overset{\rightarrow}{b}$

$(2\widehat{i} + 3\widehat{j} + 8\widehat{k})$. $( - 4\widehat{i} + 4\widehat{j} + \alpha\widehat{k})$ = 0

– 8 + 12 + 8a = 0 Ž a = $\frac{- 1}{2}$