What is the first thing you write down when doing induction?
Basis step, inductive step
What do you do in the basis step?
Show P(1) is true
What do you do in the inductive step?
Show P(k)→P(k+1) is true for all positive integers k
What is the basis step proving that for all positive integers n, it holds that n < 2ⁿ?
P(1) is true since 1 < 2¹ = 2
What is the inductive step proving that for all positive integers n, it holds that n < 2ⁿ?
Assume P(k) holds, k < 2ᵏ for an arbitrary positive integer k.
We show P(k+1) = k+1<2ᵏ⁺¹
By induction hypothesis, k<2ᵏ
Thus, k+1 < 2ᵏ+1 < 2ᵏ+2ᵏ = 2x2ᵏ = 2ᵏ⁺¹
This concludes the inductive step
What is ∑ᵏ⁺¹ᵢ₌₁ equal to by definition of summation?
∑ᵏ⁺¹ᵢ₌₁ = ∑ᵏ ᵢ₌₁ i + (k+1)