Q14 of 292 Page 549

Show that is decreasing on .

f(x)=x3+x-3


f’(x)=3x2-3x‑4


=3(x2-1/x4)




Root of f’(x)=1and-1



Here we can clearly see that f’(x) is decreasing in [-1,1]


So, f(x) is decreasing in interval [-1,1]


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