Question

find focal distance of point P on the parabola 5y² = 12x if the abscissa of P is equal to 7 

Answer 1

STEP 1 : 

Equation of parabola : 

5y² = 12x 

 y² = 12x/5 

On comparing with : 

y² = 4ax , 

4a = 12/5 , 

a = 3 /5  

STEP 2 : 

Focal distance of point P(7,y) 

= PS 

= PM ……….. FOCUS DIRECTRIX PROPERTY 

= x + a = 7 + 3/5 

= 38/5 units