
Patrick B. answered 10/06/20
Math and computer tutor/teacher
Note that for any integer M, 1 + 1/M = (M+1)/M
n=1 : 1 + 1/1 = 2
n=2: 2/1 * 3/2 = 3
n=3: 2/1 * 3/2 * 4/3 = 4
n=4: 2/1 * 3/2 * 4/3 * 5/4 = 5
n=5: 2/1 * 3/2 * 4/3 * 5/4 * 6/5 = 6
.....
n=k: 2/1 * 3/2 * 4/3 * 5/4 * 6/5 * .... * k/(k-1) * (k+1)/k = k+1 for integer k>5
and this statement serves as the induction hypothesis
So to prove the statement holds for N=k+1,
2/1 * 3/2 * 4/3 * 5/4 * 6/5 * ..... * k/(k-1) * k+1/k * ( k+2)/(k+1) =
[2/1 * 3/2 * 4/3 * 5/4 * 6/5 * ..... * k/(k-1) * k+1/k ]* ( k+2)/(k+1)
[k+1] * (k+2)/(k+1) = <--- substitutes induction hypothesis
k+2 <-- k+1 factor cancels out
end of proof