For what values of x is the rate of increase of x3−5x2+
![For what values of x is the rate of increase of x3−5x2+](/img/relate-questions.png)
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For what values of x is the rate of increase of x3−5x2+5x+8 is twice rate of increase of x ?
A.
−3,−13
B.
−3,13
C.
3,−13
D. 3,13
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Right Answer is: D
SOLUTION
Let y=x3−5x2+5x+8. Then,
dydx=(3x2−10x+5)dxdtWhendydt=2dxdt,wehave(3x2−10x+5)dxdt=2dxdt⇒3x2−10x+3=0⇒(3x−1)(x−3)=0⇒x=3,13.
Hence (d) is the correct answer.