求解 ds2

kuoyutzu

20.    1305-!-item-!-187;#058&000855

If -2x > 3y, is x negative?

 

(1) y > 0

 

(2) 2x + 5y - 20 = 0

ANS. (D)

不懂为何第二条件可??

98.    9040-!-item-!-187;#058&006792

Is x + y < 1 ?

 

(1)  x <8/9

 

(2)  y <1/8

ANS (E) 

但我觉得是c，为何??

128.  13817-!-item-!-187;#058&010140

Is y <(X+Z)/2   ?

 

(1) y - x < z - y

 

(2) z - y 

<(X+Z)/2 

ANS(D)

算不出为何第二条件可??

154.  15741-!-item-!-187;#058&010784

To install cable television in a home, a certain cable company charges a basic fee of $30 plus a fee of $20 for each cable outlet installed in the home.  How much did the cable company charge the Horace family for installing cable television in their home?

 

(1) The cable company installed three cable outlets in the Horace family home.

 

(2) The amount that the cable company charged the Horace family for installing cable television in their home was equivalent to an average (arithmetic mean) charge of $30 per cable outlet installed.

 ANS(D)

但我觉得是c，为何??

128.  13817-!-item-!-187;#058&010140

Is y <(X+Z)/2   ?

 

(1) y - x < z - y

 

(2) z - y 

<(X+Z)/2 

ANS(D)

算不出为何第二条件可??

154.  15741-!-item-!-187;#058&010784

To install cable television in a home, a certain cable company charges a basic fee of $30 plus a fee of $20 for each cable outlet installed in the home.  How much did the cable company charge the Horace family for installing cable television in their home?

 

(1) The cable company installed three cable outlets in the Horace family home.

 

(2) The amount that the cable company charged the Horace family for installing cable television in their home was equivalent to an average (arithmetic mean) charge of $30 per cable outlet installed.

 ANS(D)

sheibiwosha

题目好多，先来第一题

If -2x > 3y, is x negative?

 

 

(1) y > 0

 

 

(2) 2x + 5y - 20 = 0

y=(20-2x)/5，代入-2x>3y即可得出x<-15

y=(20-2x)/5，代入-2x>3y即可得出x<-15