Question:
52n+2 −24n −25 is divisible by 576 for all n ∈ N.
Solution:
Let P(n) be the given statement.
Now,
$P(n): 5^{2 n+2}-24 n-25$ is divisible by 576 for all $n \in N$.
Step 1:
$P(1)=5^{2+2}-24-25=625-49=576$
It is divisible by 576 .
Thus, $P(1)$ is true.
Step 2 :
Let $P(m)$ be true.
Then,
$5^{2 m+2}-24 m-25$ is divisible by 576
Let $5^{2 m+2}-24 m-25=576 \lambda$, where $\lambda \in N$.
We need to show that $P(m+1)$ is true wheneve $r P(m)$ is true.
Now,
$P(m+1)=5^{2 m+4}-24(m+1)-25$
$=5^{2} \times(576 \lambda+24 m+25)-24 m-49$
$=25 \times 576 \lambda+600 m+625-24 m-49$
$=25 \times 576 \lambda+576 m+576$
$=576(25 \lambda+m+1)$
It is divisible by 576 .
Thus, $P(m+1)$ is true
By the principle of $m$ athematical $i$ nduction, $P(n)$ is true for all $n \in N$.