Question
The straight line x + y = k touches the parabola y = x – x2, if k =
- 0
- – 1
- 1
- None
Hint:
replace the value of y into the equation of parabola and solve the resulting equation.
The correct answer is: 1
k=1
Given, X+y=k
y=k-x
and y=x-x2
=> k-x = x-x2
since the line touches the curve,
D =0
b2-4ac=0
4-4k=0
4k=4
k=1
since only one point of contact is present, D=0 gives the real root.
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