1+.

Let P(n) = 1+.
P(1) is true
Let P (k) be true.
P(k) = 1+
To Prove P(K+1) is true using P(k) Lies
1+
                                                                    = ……… (1)
L.H.S of (1)

                                                                            =
                                                                                Taking L.c.M
                                                                            =
                                                                            =
                                                                            = =
                                                                            = R.H.S of (1)
P(K+1) is true.
By the Principle of mathematical induction, P(n) is true for all values of n where n N
Hence proved.