Question

The ordinate of point P on the parabola y² = 16x is 8 . Find focal distance of point P

Answer 1

STEP 1 : 

Equation of parabola : y² = 16x 

On comparing with : y² = 4ax , 4a = 16 , a = 4 

STEP 2 : 

P(x , 8) lies on parabola y² = 16x & hence it must satisfy the equation of parabola 

∴ 8² = 16x 

x = 4 , P(4,8) 

STEP 3 : 

Focal distance of point P(4,8) = PS 

= PM ……….. FOCUS DIRECTRIX PROPERTY 

= x + a 

= 4 + 4 

= 8 units