Bunuel Just to confirm, when we don't know the sign of a variable we don't cross multiply. This rule is only applicable with inequalities, right? Otherwise i'm confused as to how you did it in your explanation!
The easier way to solve this is to test numbers that satisfy the stem:
If S and T are non-zero then they can either be positive/ negative or both.
Case 1: S and T are both positive
S= 1
T = 1
1/1 + 1/1 = 1+1
2=2
Satisfies
Case 2: S and T are both negative
S=-1
T=-1
1/-1 +1/-1 = -1+-1
-1 -1 = -2
Yes, satisfies
Case 3: S = positive, T = Negative
S = 1
T= -1
1/1 + (1/-1)= 1 -1
1 -1 = 1-1
Yes, Satisfies
Case 4: S and T are positive proper fractions
1/(1/2) + 1/(1/2) = 1/2 + 1/2
2+2 = 1? NO Does not satisfy -->same for negative fractions
Using the above we can POE:
A - could be true but doesn't HAVE to be true as per case 3
B - Not necessarily, can also equal 0
C - No, as we learned S can be positive, T can be negative
D - No, same reasoning as C
E is our answer.
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Goal: Q49, V41
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