IGDTUW 2025 — Mathematics PYQ
IGDTUW | Mathematics | 2025If the four distinct points (4,6), (−1,5), (0,0) and (k,3k) lie on a circle of radius r, then 10k+r2 is equal to:
Choose the correct answer:
- A.
32
- B.
33
- C.
34
- D.
35
(Correct Answer)
35
Explanation
Solution:
Let the circle equation be x2+y2+2gx+2fy+c=0.
Since it passes through (0,0), we find c=0.
Plugging in (4,6) and (−1,5), we get a system of equations that yields the center (−g,−f)=(2,3).
The radius squared is r2=22+32=13.
Since (k,3k) lies on the circle: k2+(3k)2+2(−2)k+2(−3)(3k)=0.
This simplifies to 10k2−22k=0. Since the points are distinct (k=0), k=1022=2.2.
Calculate the final value: 10k+r2=10(2.2)+13=22+13=35.
Correct Option: (d)
Explanation
Solution:
Let the circle equation be x2+y2+2gx+2fy+c=0.
Since it passes through (0,0), we find c=0.
Plugging in (4,6) and (−1,5), we get a system of equations that yields the center (−g,−f)=(2,3).
The radius squared is r2=22+32=13.
Since (k,3k) lies on the circle: k2+(3k)2+2(−2)k+2(−3)(3k)=0.
This simplifies to 10k2−22k=0. Since the points are distinct (k=0), k=1022=2.2.
Calculate the final value: 10k+r2=10(2.2)+13=22+13=35.
Correct Option: (d)

