Is #f(x)=(-x-4)^2+3x^2-3x # increasing or decreasing at #x=-1 #?

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Answer 1 · 2016-05-06T14:29:49

#f(x)=(-x-4)^2+3x^2-3x# is decreasing at #x=-1#

From the given equation, obtain the first derivative and then substitute the value of #x=-1#
#f(x)=(-x-4)^2+3x^2-3x#

#f(x)=x^2+8x+16+3x^2-3x#

#f(x)=4x^2+5x+16#

#f'(x)=8x+5#

#f'(-1)=8(-1)+5#

#f'(-1)=-3" "#this means decreasing

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