© examsiri.com
Question : 74 of 150
Marks:
+1,
-0
Solution:
‌f(x)=a⋅(b×c)‌‌‌=||‌=x(x2−2)+2(−2x+7)+3(4−7x)‌∴‌‌f(x)=x3−27x+26 Now,
f′(x)=0‌⇒3x2−27=0‌⇒x2=9‌⇒x=±3‌f′′(x)=6x‌⇒f′′(x)=18>0 ‌f(x) has local minimum at
x=3‌∴‌‌a=3−2+3‌b=−2+3−‌∴‌‌a⋅b=(3−2+3)⋅(−2+3−)‌=3(−2)+(−2)(3)+3(−1)‌=−15‌
© examsiri.com
Go to Question: