Most Important Selected Qs for JEE AdvancedMathematicsApplication of Derivatives
Let f^ (x) be a continuous function which maps from [0,1] [p(a), p(b)] . If p(x) is a differentiable function on [a, b] such that p(g(x))=x, g(0)=a and g(1)=b , then which of the following is/are true?
Options
- Af^ (0)+2 < f(1)
- Bf(1) 1+f(0)
- C₀^1 f^ (x) d x ₀^1 g^ (x) d x p^ (c) for some c (a, b)
- DThere exists k [0,1] such that f^ (k)=k
Correct answer
D. There exists k [0,1] such that f^ (k)=k
Step-by-step solution
First observe that g is the inverse of p . Hence p(a)=0, p(b)=1 . Also f^ is a continuous function which maps from [0,1] [0,1] by Intermediate value theorem we can say that there is k [0,1] such that f^ (k)=k ( d ) Now, f^ (x) 1 (p(b)-p(a)) Hence, ₀^1 f^ (x) d x (p(b)-p(a)) Divide both sides by b-a= ₀^1 g^ (x) d x ₀^1 f^ (x) d x ₀^1 g^ (x) d x (p(b)-p(a)) b-a =p^ (c), c (a, b) [ By LMVT] (c) Also, use LMVT for y=f(x) in [0,1] f^ (c)= f(1)-f(0) 1-0 1f(1)-f(0) 1f(1) 1+f(0) (b)