integers

[ketkoag]

for integers a and b if (a^3 - a^2 - b)^.5 = 7,
what is the value of a?
1)a^2 - a =12
2)b^2 - b = 2

OA: b

[SanjeevK]

IMO B:
(a^3 - a^2 - b)^.5 = 7
or (a^3 - a^2 - b) = 49

A: a^2 - a =12 => a^2 - a - 12 = 0 => a = 4 or a = -3. Not sufficient
B: b^2 - b = 2 => b = 2 or b = -1
if b = 2, a^3 - a^2 = 51. This doesn't give an integer value for a.
if b = -1, a^3 - a^2 = 48 => a = 4. Sufficient

Hope this helps

[abhinav85]

IMO B as well...........

[joymukhi]

Hi there..isnt b(b-1) = 2 in this case? b shud be 2 or 3 right?

[joymukhi]

Apologies & shame on me ..disguised quads ..shame on me ignore my previous post mates.