In how many ways can 8192 be written as a difference of two perfect squares?
a) 6
b) 7
c) 13
d) 14
why the answer is 6 and not 7?
a) 6
b) 7
c) 13
d) 14
why the answer is 6 and not 7?
If 8192 is expressed as a difference of two perfect squares a² and b², then,MBA.Aspirant wrote:In how many ways can 8192 be written as a difference of two perfect squares?
- 8192 = (a² - b²) = (a - b)(a + b)
Now, 8192 = 2^13
Hence, 8192 can be factored as any one of the following seven ways,
- 2^1 x 2^12
2^2 x 2^11
2^3 x 2^10
2^4 x 2^9
2^5 x 2^8
2^6 x 2^7
1 x 8192
Hence, 8192 can be written as a difference of two perfect squares in 6 different ways.
The correct answer is A.
Note 1: 1 x 8192 cannot be expressed as (a - b)(a + b) because if we do so we'll get non-integer values for a and b.
Note 2: Here is an example how others can result a way to express 8192 as a difference of two perfect squares. For example take the factorization, 8192 = 2^3 x 2^10 = 8*1024 = (a - b)(a + b)
Hence, (a - b) = 8 and (a + b) = 1024
Hence, a = 516 and b = 508
Thus, 8192 = (516)² - (508)²
