Application of Derivatives 4 Question 27

####28. If y=alogx+bx2+x has its extremum values at x=1 and x=2, then

(a) a=2,b=1

(b) a=2,b=12

(c) a=2,b=12

(d) None of the above

(1983,1M)

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Answer:

Correct Answer: 28. (a,b,c,d)

Solution:

  1. y=alogx+bx2+x has extremum at x=1 and x=2.

dydx=0, at x=1

 and x=2ax+2bx+1=0, at x=1 and x=2a2b+1=0 and a2+4b+1=0a=2 and b=12



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