All of the following expressions have the same value, when x = -2 and y = 4, except a) x 2y ) 2y c)-4x 2 d)-2xy

The correct answer is:  [D]:  " - 2xy " .


Explanation:

Let us consider the value of each of the answer choices; 

Given:  " x = -2 " ;  and:  " y = 4 " ;  

Choice [A]:    "  x * 2y  =  -2 * (2 * 4)  =  -2 * 8  =  -16  .

Choice [B]:    " (-2)* (2y) = (-2) * (2 * 4)  =  -2 * 8  =  -16  .

Choice [C]:    " -4x * 2 =  -4(-2) * 2 = -8 * 2  = -16

Choice [D]:    " -2xy  =  (-2 * -2 * 4)  = 4 * 4 = 16.


→ The answer is:  Choice [D]:  " -2xy " .


→  When "x = -2 " ; and "y = 4" ;  

→  Answer choices [A], [B], and [C] have the same value:  " -16 " .

→  Answer choice [D]:  The value is different:  "16" {"positive 16" .}.