COMEDK2014MathematicsMathematical Induction
7⁹+9⁷ is divisible by
Options
- A128
- B24
- C64
- D72
Correct answer
C. 64
Step-by-step solution
Now, 7⁹=(8-1)⁹=-1(1-8)⁹=-1+ 9 1 8- 9 2 8²+ + 9 9 8⁹ and 9⁷=(1+8)⁷=1+ 7 1 8+ 7 2 8²+ 7 3 8³+ .+ 7 7 8⁷ 7⁹+9⁷=8 ( 9 1 + 7 1 )+8² ( 7 2 - 9 2 )+ =8(9+7)+8²(21-36)+ =64 2+64(-15)+ Hence, it is divisible by 64 .