Applications Of Derivatives Question 157
Question: If $ x+y=10 $ , then the maximum value of xy is
Options:
A) 5
B) 20
C) 25
D) None of these
Show Answer
Answer:
Correct Answer: C
Solution:
$ x+y=10; $
$ \therefore y=10-x $ …………..(i) Now $ f(x)=xy=x(10-x)=10x-x^{2} $
$ \therefore f’(x)=10-2x $
For maximum value of $ f(x),,f’(x)=0 $
$ \therefore x=5 $ and $ y=5 $
So maximum value of $ xy=5\times 5=25 $ .
BETA
