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Question

lf f(x) is a quadratic expression which is positive for all real vaues of x and g(x)=f(x)+f(x)+f′′(x) then for any real value of x
  1. g(x)>0
  2. g(x)<0
  3. g(x)=0
  4. g(x)>0

A
g(x)<0
B
g(x)>0
C
g(x)=0
D
g(x)>0
Solution
Verified by Toppr

Let f(x)=ax2+bx+c
According to the given condition a>0,b24ac<0.........(i)
g(x)=ax2+bx+c+2ax+b+2a=ax2+(b+2a)x+(b+c+2a)
Now discriminant of g(x) is D=(b+2a)24a(2a+c+b)=b2+4a2+4ab4ab4ac8a2=(b24ac)4a2<0 using (i)
Hence g(x)>0 for any xR

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