Explanation
Step 1: Parabola ki equations ko standard form mein likhein
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Pehli curve: y2=21x. Yeh y2=4ax jaisa hai, jahan 4a=1/2⟹a=1/8.
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Doosri curve: y2=x−1. Yeh shifted parabola hai.
Step 2: Dono ke liye tangent ki equation likhein
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Pehle parabola (y2=2x) ke liye tangent:
y=mx+ma⟹y=mx+8m1—(Equation 1)
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Doosre parabola (y2=x−1) ke liye tangent:
Shifted parabola ke liye hum x ko (x−1) se replace karenge:
Yahan 4a′=1⟹a′=1/4.
y=m(x−1)+4m1⟹y=mx−m+4m1—(Equation 2)
Step 3: Common tangent ke liye c ko compare karein
Dono equations ek hi line ko represent karti hain, isliye inka constant part barabaar hona chahiye:
Sari terms ko 8m se multiply karne par:
1=−8m2+2
8m2=1⟹m2=1/8⟹m=81=221
(Kyunki sawal mein m > 0 diya gaya hai).
Step 4: Common tangent ki equation nikalna
m ki value Equation 1 mein rakhein:
y=221x+8(1/22)1=22x+822=22x+42
L.C.M lene par (22×2=4, toh base 42 ban sakta hai):
42y=2x+2
Step 5: Point (6,−22) se perpendicular distance (d)
d=12+(−22)2∣x1−22y1+1∣
Final Answer:
Distance 5 unit hai. Sahi option (4) hai.