Q30 of 105 Page 17

Prove that the following function is increasing on r?

i. f(x) = 3x5 + 40x3 + 240x


ii. f(x) = 4x3 – 18x2 + 27x – 27

(i) we have

f(x) = 3x5 + 40x3 + 240x





Now,


xR





Hence, f(x) is an increasing function for all x


(ii) we have


f(x) = 4x3 – 18x2 + 27x – 27





Now,


x R





Hence, f(x) is an increasing fuction for all x


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