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Find the interval on which the function f(x)=x²+5x²+8x+1 is a strictly increasing function |
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Answer» ehave,F(x)= 4x 4 −x 3 −5x 2 +24x+12⇒f ′ (x)=x 3 −3x 2 −10x+24⇒f ′′ (x)=3x 2 −6x−10Iff ′′ (x)>0thefunctionisstrictlydecreasingandiff ′′ (x)<0⇒3x 2 −6x−10=0⇒x= 66± 36+4×3×10 = 66± 156 = 66±12.4899 ⇒x=3.08or−1.08Wegetthatf ′′ (x)<0when−1.08 |
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