AP EAMCET · Maths · Parabola

If $a x + b y = 1$ is a normal to the parabola $y^{2} = 4 p x$ then the condition is

A $4 a b = a^{2} + b^{2}$
B $4 p a b + a b^{3} = a^{2} b^{2}$
C $p a^{3} = b^{2} - 2 p a b^{2}$
D $p a^{2} + 1 p a = a + b$

Verified Solution

Answer & Solution

Correct Answer

(C) $p a^{3} = b^{2} - 2 p a b^{2}$

Step-by-step Solution

Detailed explanation

For the parabola y2=4px, the equation of normal is y=mx-2pm-pm3. Comparing it with the given equation of normal y=-abx+1b, we get -ab=m; -2pm-pm3=1b i.e. -2p-ab-p-ab3=1b ⇒2pab+pa3b3=1b⇒2pab2+pa3=b2

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Explore more questions on app

From AP EAMCET

Explore more questions on app

If ax+by=1 is a normal to the parabola y2=4px then the condition is

Step-by-step Solution

If $a x + b y = 1$ is a normal to the parabola $y^{2} = 4 p x$ then the condition is