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Question: Answered & Verified by Expert
A particle moves along the curve $y=x^2+2 x$. Then, the point on the curve such that $x$ and $y$ coordinates of the particle change with the same rate is
MathematicsApplication of DerivativesTS EAMCETTS EAMCET 2004
Options:
  • A $(1,3)$
  • B $\left(\frac{1}{2}, \frac{5}{2}\right)$
  • C $\left(-\frac{1}{2},-\frac{3}{4}\right)$
  • D $(-1,-1)$
Solution:
2565 Upvotes Verified Answer
The correct answer is: $\left(-\frac{1}{2},-\frac{3}{4}\right)$


Given equation of curve is
$$
y=x^2+2 x
$$
On differentiating both sides w.r.t. $t$, we get
$$
\frac{d y}{d t}=(2 x+2) \frac{d x}{d t}
$$

$$
\begin{aligned}
\Rightarrow & & 2 x & =-1 \\
\Rightarrow & & x & =-1 / 2, y=-3 / 4
\end{aligned}
$$
$\therefore$ Point on the curve is $\left(-\frac{1}{2},-\frac{3}{4}\right)$.

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