For f(x)=x^3-39x, on which interval is the function increasing?
f(x)=x^3-39x किस interval में increasing है?
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Correct Answer
C. (-infinity,-3) union (3,infinity)
ExplanationStep 1: f'(x)=3x^2-39=3(x^2-9). Step 2: f'(x)>0 when |x|>3, so the increasing intervals are outside the roots. Step 3: tip: positive derivative means increasing function.
Step 1: f'(x)=3x^2-39=3(x^2-9) है। Step 2: f'(x)>0 when |x|>3, इसलिए increasing intervals outside roots हैं। Step 3: tip: derivative positive means function increasing।