Equation of Tangent at a Point (x,y) in Terms of f'(x)
If y = fx b...
Question
If y=f(x) be the equation of a parabola which is touched by the line y=x at the point where x=1 Then
A
f′(1)=1
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B
f′(0)=f′(1)
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C
2f(0)=1−f′(0)
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D
f(0)+f′(0)+f"(0)=1
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Solution
The correct options are C2f(0)=1−f′(0) Df′(1)=1 Let, y=ax2+bx+c ∴y′=2ax+b Given line y=x touches this parabola at x=1 ⇒y(1)=1⇒a+b+c=1..(1) and y"(1)=1⇒2a+b=1..(2) Solving (1) and (2) we get 2c=1−b⇒2f(0)=1−f′(0)