Given f ( x ) = x 3 - 4 x , if x changes from 2 to 1 . 99 , then the approximate change in the value of f (…

Given f(x)=x3-4x, if x changes from 2 to 1.99, then the approximate change in the value of f(x) is
  1. 0.08
  2. −0.08
  3. 0.8
  4. −0.8

Solution

Let, y=x3-4x,

Since, we have x=2 and ∆x=-0.01

Now, dydx=3x2-4 ⇒dydxx=2=3x2-4x=2=8

So, ∆y=dydx∆x=8×-0.01=-0.08

Asked in: MHT CET Full Test 13

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