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NARAYANA IIT/PMT ACADEMY - Narayanaicc.com

NARAYANA IIT/PMT ACADEMY - Narayanaicc.com

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<strong>NARAYANA</strong> <strong>IIT</strong>/<strong>PMT</strong> <strong>ACADEMY</strong><br />

JEE ADVANCE : 2013<br />

(PAPER – II) CODE: 0<br />

(0, 3)<br />

(0, 3)<br />

E<br />

G<br />

0, 0<br />

F(x , y )<br />

0 0<br />

(0, y ) 1<br />

2<br />

y =16x<br />

Let Co-ordinate of F= (x 0 , y 0 ) = (4t 2 8t)<br />

Co-ordinate of E = (0, 3) ……… given<br />

Equation of tangent at F ty = x + 4t 2<br />

Co-ordinate of G (0, 4t)<br />

0 3 1<br />

Area of EFG<br />

1 0 4 t 1<br />

2 4<br />

2<br />

t 8 t 1<br />

1 12 2 3<br />

t t<br />

2<br />

Let<br />

t<br />

1 12<br />

2 16<br />

3<br />

t t<br />

2<br />

' t<br />

1<br />

2<br />

24t 48t<br />

2<br />

' t 0 t<br />

1<br />

2<br />

" t<br />

1<br />

24<br />

2<br />

96t<br />

"<br />

1 1 1<br />

24 96<br />

2 2 2<br />

12<br />

Since (4t 2 , 8t) lies on the lie y = mx + 3<br />

8t<br />

3<br />

m<br />

2<br />

4t<br />

1<br />

at t , t will be maximum<br />

2<br />

2<br />

8t 4mt<br />

3<br />

At t = 1 2<br />

We get 1 m<br />

Maximum area will be at t = 1/2<br />

maximum area of triangle = 1/2<br />

y 0 = 8t = 4<br />

y 1 = 4t = 2<br />

<strong>NARAYANA</strong> GROUP OF EDUCATIONAL INSTITUTIONS - INDIA<br />

39

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