stA is not sufficient(r ^ 2-s ^ 2) ^ 2 =?
A. 4R ^ 2S ^ 2 = 120
B: (R ^ 2 + S ^ 2) ^ 2 = 4R ^ 2S ^ S
St B is sufficient.
(r^2 - s^2)^2 = (r^2 + s^2)^2 -4r^2s^2 = 0
[(a -b)^2 = (a + b)^2 - 4ab]
189) Find the value
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Source: Beat The GMAT — Data Sufficiency |
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indiantiger
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(r ^ 2-s ^ 2) ^ 2 =?
1. 4R ^ 2S ^ 2 = 120
2: (R ^ 2 + S ^ 2) ^ 2 = 4R ^ 2S ^ S
expand (r ^ 2-s ^ 2) ^ 2 = r^4+s^4-2r^2s^2
Too me 2 looks simple to start with will pick B first
expand B) R^4+S^4+2R^2*S^2-4R^2*S^2=0
R^4+S^4-2R^2S^2 = (R^2-S^2)^2=0
Now we can get rid off choices C and E
lets check for 1
which gives us partial information so answer is B
1. 4R ^ 2S ^ 2 = 120
2: (R ^ 2 + S ^ 2) ^ 2 = 4R ^ 2S ^ S
expand (r ^ 2-s ^ 2) ^ 2 = r^4+s^4-2r^2s^2
Too me 2 looks simple to start with will pick B first
expand B) R^4+S^4+2R^2*S^2-4R^2*S^2=0
R^4+S^4-2R^2S^2 = (R^2-S^2)^2=0
Now we can get rid off choices C and E
lets check for 1
which gives us partial information so answer is B
