Application of DerivativeHard
Question
If the line ax + by + c = 0 is a normal to the curve xy = 1, then
Options
A.a > 0,b > 0
B.a > 0,b < 0
C.a < 0,b > 0
D.a < 0,b < 0
Solution
Given, xy = 1 ⇒ 
Thus slope of normal = x2 (which is always positive) and it is given ax + by + c = 0 is normal whose slope = -
⇒
or 
∴ a and b are of opposite sign.
Thus slope of normal = x2 (which is always positive) and it is given ax + by + c = 0 is normal whose slope = -
⇒
or ∴ a and b are of opposite sign.
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