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Question Number 95560 by I want to learn more last updated on 26/May/20

Commented by i jagooll last updated on 26/May/20

y=(x^2 +5)^(−1)    y^′  = ((−2x)/((x^2 +5)^2 )) ≥ 0   increasing for x ≤ 0   decreasing for x ≥ 0

y=(x2+5)1y=2x(x2+5)20increasingforx0decreasingforx0

Answered by mr W last updated on 26/May/20

y′=−((2x)/((x^2 +5)^2 ))  y increases or decreases most rapidly  means y′ is maximum or minimum,  that means again y′′=0.  y′′=−(2/((x^2 +5)^2 ))+((4x^2 )/((x^2 +5)^3 ))=0  2x^2 =x^2 +5  ⇒x=±(√5)  at x=−(√5): y′>0, y increases most rapidly.  at x=(√5): y′<0, y decreases most rapidly.

y=2x(x2+5)2yincreasesordecreasesmostrapidlymeansyismaximumorminimum,thatmeansagainy=0.y=2(x2+5)2+4x2(x2+5)3=02x2=x2+5x=±5atx=5:y>0,yincreasesmostrapidly.atx=5:y<0,ydecreasesmostrapidly.

Commented by I want to learn more last updated on 26/May/20

thanks sir

thankssir

Commented by peter frank last updated on 26/May/20

thank you

thankyou

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