y = x^2 + 6x 7, x= 1). x is positive integer 2). y^2=y

Question

y = x^2 + 6x – 7, x= 

1). x is positive integer

2). y^2=y

rkatl · Answer

why not 'A'

from the stem, x = -7 or 1 

and A says x has to be +ve then x must be 1 ?

trivikram · Answer

here the eq is not =0 but equal to y.

How can you deduce anything from 1 only?

either it has to be C or E

ps_dahiya · Answer

C

St1: clearly INSUFF

St2: y = 0 or y = 1.
then there are two equations
x^2 + 6x-7 = 0 gives us x = 1 or -7 and
x^2+6x-8 = 0 gives us two non-integer roots.: INSUFF

Together:
x = 1.: SUFF

yezz · Answer

the key here is statment b

y^2 =y thus y is either = {-1,1,0}....insuff

both together

x is positive and y = x^2 + 6x â€“ 7

if y = -1 thus x^2 + 6x-6 = 0....this equation has two non intiger answers one +ve and one -ve ( test with (b^2 - 4ac)....insuff

y = 1 thus x^2 + 6x-8 = 0 this equation has non intiger answers one +ve and one -ve....insuff

if y = 0 the equation has two intiger roots and as it is mentioned in one that x is positive intiger 

thus C is my answer

y = x^2 + 6x 7, x= 1). x is positive integer 2). y^2=y

Prep Toolkit

Top 5 GMAT Debrief Videos

615 to 715 in 15 Days (Ria's Strategies)

More than Quant/Verbal Abilities: Speed vs. Accuracy

745 with Only Self-Prep and GMAT Club

From 555 to 765: 210-point Improvement

Perfect 805 Score Debrief by Julia

My Rewards