Question
If the line x + y –1 = 0 touches the parabola y2 = kx, then the value of k is-
- 2
- –4
- 4
- –2
Hint:
compare the equation of tangent of parabola with the given equation of line.
The correct answer is: –4
k=-4
given, x+y-1 = 0 touches parabola y2 = kx,
y =-x+ 1 is tangent to y2 = kx
a=k/4
c=a/m
1= k/-4
k=-4
we can also solve for the two lines and make the D=0 for the resultant quadratic equation.
Related Questions to study
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