【SAT每日一】7/23/12 Mathematics > Standard Multiple Choice

滚吧肥汤圆UID: 3272378

Read the following SAT test question and then click on a button to select your answer.
+ Q; L/ Z  P. _% x" F) d
If , which of the following statements must also be true?
" b2 @: E+ A+ ~2 r. B& S
9 z8 a: n2 e4 h' K .
" |0 H  m% h& C& v! r7 K* n$ r- g5 D" c
.
$ i/ R; Q) E( d: F3 c% i" h
" ]1 X0 e- w2 w( |2 V* z# F( B
% d4 x+ K/ i, _% H0 I
.

' F$ L) O& c$ M" j6 K3 R
9 E2 t  |; V3 q2 }9 \" I2 K& G7 [
7 S/ [7 p- z9 V

1 c& @3 U$ ^3 {2 G! t* D8 VA. None
0 o9 Q6 T$ `+ n7 H& c# h
# \3 w; X& \  D/ l6 q: h! oB.   only

C.   only

D.   only

& T: W9 X9 W; }* j  z+ AE.   and  
% m% f; A8 j; X9 ^
  o. J7 d& R' X( O/ C) n正确答案:E

解析:
6 u. g  m( B0 ^1 s
2 |( G4 i" {/ u6 @/ WThe quantity   can be expressed as  .
1 }  o  X  q7 j! c% [) EIf , then  and  .
Since  , either   or or both. Therefore,
statement must be true, but statement , ,
is not always true. For statement , you can write
, and since ,
it follows that .
, z6 L+ w+ R* i8 A4 D! g! OTherefore, both statements and must be true.