Question:

If the normal at $(ap^2, 2ap)$ on the parabola $y^2 = 4ax,$ meets the parabola again at $(aq^2, 2aq)$, then

Updated On: Aug 18, 2024
  • $p^2 + pq + 2 = 0 $
  • $p^2 - pq + 2 = 0$
  • $q^2 + pq + 2 = 0$
  • $p^2 + pq + 1 = 0$
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The Correct Option is A

Solution and Explanation

Since the normal at $(ap^2, 2ap)$ on $y^2 = 4ax$ meets the curve again at $(aq^2, 2aq)$, therefore $px + y = 2ap + ap^3$ passes through $(aq^2,2aq)$
$\Rightarrow \; paq^2 + 2aq = 2ap + ap^3$ $\Rightarrow \; p(q^2-p^2) = 2(p - q)$ $\Rightarrow \; p (q + p) = -2$ $\Rightarrow \; p^2 + pq + 2 = 0$
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Concepts Used:

Arithmetic Progression

Arithmetic Progression (AP) is a mathematical series in which the difference between any two subsequent numbers is a fixed value.

For example, the natural number sequence 1, 2, 3, 4, 5, 6,... is an AP because the difference between two consecutive terms (say 1 and 2) is equal to one (2 -1). Even when dealing with odd and even numbers, the common difference between two consecutive words will be equal to 2.

In simpler words, an arithmetic progression is a collection of integers where each term is resulted by adding a fixed number to the preceding term apart from the first term.

For eg:- 4,6,8,10,12,14,16

We can notice Arithmetic Progression in our day-to-day lives too, for eg:- the number of days in a week, stacking chairs, etc.

Read More: Sum of First N Terms of an AP