Let the function f: [1, ∞) → R be defined by f(t) = (-1)ⁿ⁺¹2, if t = 2n-1, n ∈ N,
((2n+1-t))/2 f(2n-1) + ((t-(2n-1)))/2 f(2n+1), if 2n-1 < t < 2n+1, n ∈ N. Define g(x) = ∫₁ˣ f(t) dt, x ∈ (1, ∞). Let α denote the number of solutions of the equation g(x) = 0 in the interval (1, 8] and β = lim_(x → 1⁺) g(x)/(x-1). Then the value of α + β is equal to ____.
f(2n−1)=(−1)n+12
f is linear on [2n−1,2n+1]
g(x)=∫1xf(t)dt
α=#{x∈(1,8]:g(x)=0}
β=limx→1+x−1g(x)
find α+β
1. f on each interval (linear)
2. g(x)=∫1xf, find its zeros
3. β=g′(1)=f(1)
f(t)=4−2t,t∈[1,3]
f(t)=2t−8,t∈[3,5]
f(t+4)=f(t)⇒period 4
g(x)=∫1x(4−2t)dt=4x−x2−3
g(2)=1,g(3)=0
g(x)=∫3x(2t−8)dt=x2−8x+15
g(4)=−1,g(5)=0
g(x+4)=g(x)
g=0 at x=3,5,7∈(1,8]
α=3
β=limx→1+x−1g(x)=g′(1)=f(1)=2
α+β=3+2=5
5