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AP EAMCET · Maths · Application of Derivatives

The curve \(y=a x^3+b x^2+c x+5\) touches \(X\)-axis at \(P(-2,0)\), then \(c=\)

  1. A \(4 a+5\)
  2. B \(4 a-5\)
  3. C \(5-4 a\)
  4. D \(0\)
Verified Solution

Answer & Solution

Correct Answer

(A) \(4 a+5\)

Step-by-step Solution

Detailed explanation

\(y=a x^3+b x^2+c x+5\) ...(i) \(\because\) It passes through \((-2,0)\) \(\therefore \quad 0=-8 a+4 b-2 c+5\) ...(ii) \(\begin{aligned} & \Rightarrow \frac{d y}{d x}=3 a x^2+2 b x+c \\ & \Rightarrow\left[\frac{d y}{d x}\right]_{(-2,0)}=12 a-4 b+c\end{aligned}\) According to…