Prove the following by using the principle of mathematical induction for all
a + (a + d) + (a + 2d) + ...........+ [a + (n - 1)d] =
Prove the following by using the principle of mathematical induction for all
n (n + 1) (n + 5) is a multiple of 3.
Prove the following by using the principle of mathematical induction for all
is a multiple of 27 for all
Prove the following by using the principle of mathematical induction for all
is divisible by 11.
Prove the following by using the principle of mathematical induction for all
is divisible by 8.
Let is divisible by 8.
I.     For n = 1,
     P(1) : is divisible by 8
 is divisible by 8 81 - 17 is divisible by 8 64 is divisible by 8
     which is true
∴    P(n) is true for n = 1
II.   Let the statement be true for n = m,
∴    is divisible by 8
   ...(i)
III.    For n = m + 1,
       is divisible by 8
Now,  Â
= Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â [By (i)]
= 72k + 72m + 81 - 8m - 17 = 72k + 64m + 64 = 8(9k + 8m + 8),
= 8k'Â where k' = 9k + 8m +
∴    is divisible by 8.
 P(m + 1) is true.
∴  P(m) is true P (m + 1) is true.
Hence, by the principle of mathematical induction, P(n) is true for all
Prove by mathematical induction that sum of cubes of three consecutive natural numbers is divisible by 9.