Q.

Let the parabola y=x2+px–3, meet the coordinate axes at the points P, Q and R. If the circle C with centre at (–1, –1) passes through the points P, Q and R, then the area of △PQR is :          [2025]

1 7  
2 4  
3 6  
4 5  

Ans.

(3)

Given, equation of parabola is y=x2+px–3 and equation of circle with centre at (–1, –1) is

         (x+1)2+(y+1)2=r2          ... (i)

Let P(α, 0), Q(β, 0) and R(0, –3) are the three points.

Now, circle passes through point R(0, –3)

⇒ 1+(–2)2=r2 ⇒ 5=r2

Put y = 0 in equation (i), we get

         (x+1)2+1=5

⇒ (x+1)2=4 ⇒ x=1 or x=–3

⇒ Point are P(1, 0) and (–3, 0)

∴  Area of △PQR=12|101–3010–31|=6 sq. units