Gujarat BoardEnglish MediumSTD 11 ScienceMATHSPRINCIPLE OF MATHEMATICAL INDUCTION1 Mark
MCQ
For every positive integer $n, 7^n-3^n$ is divisible by:
A
3
✓
4
C
7
D
5
✓
Answer
Correct option: B.
4
4
Solution:
Let $P(n)=7^n-3^n$
Substituting $\mathrm{n}=1,2,3, \ldots$
$P(1)=7^1-3^1=7-3=4$
$P(2)=7^2-3^2=49-9=40$
$P(3)=7^{3-} 3^3=343-27=316$
Thus, for every positive integer $n, 7^n-3^n$ is divisible by 4 .
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