Vector Algebra Question 298
Question: If $ |\mathbf{a}|=3,,|\mathbf{b}|=4 $ and $ |\mathbf{a}+\mathbf{b}|=5, $ then $ |\mathbf{a}-\mathbf{b}|= $
[EAMCET 1994]
Options:
A) 6
B) 5
C) 4
D) 3
Show Answer
Answer:
Correct Answer: B
Solution:
- We have $ |\mathbf{a}+\mathbf{b}{{|}^{2}}+|\mathbf{a}-\mathbf{b}{{|}^{2}}=2(|\mathbf{a}{{|}^{2}}+|\mathbf{b}{{|}^{2}}) $
$ \therefore ,25+|\mathbf{a}-\mathbf{b}{{|}^{2}}=2(9+16)\Rightarrow |\mathbf{a}-\mathbf{b}|=5 $ .
BETA
