Is y = 6?
1. y^2 = 36
You have either y=6 or y=-6
So it is insufficient.
2. y^2- 7y + 6 = 0
We can write it like that
(y-6)(y-1)=0
So here the solutions are either y=6 or y=1
So it is insufficient.
1 and 2.
y=6 or y=-6 and y=6 or y=1
So it is 6 !
C
equations
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Source: Beat The GMAT — Data Sufficiency |
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pepeprepa
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In this case, you cannot chose y=1 or y=-6
You can see
that for y=1, y^2 is different from 36
for y=-6, y^2- 7y + 6 is different from 0
But with y=6 we have y^2 = 36 and y^2- 7y + 6 = 0
What you look is a solution which suits both statements, your solution cannot contradict with one equation but be wrong with another equation. You should practice DS questions to be used to what they ask you.
You can see
that for y=1, y^2 is different from 36
for y=-6, y^2- 7y + 6 is different from 0
But with y=6 we have y^2 = 36 and y^2- 7y + 6 = 0
What you look is a solution which suits both statements, your solution cannot contradict with one equation but be wrong with another equation. You should practice DS questions to be used to what they ask you.
