GMAT考试

【单选题】If x, y, and z are positive integers and x²=y²+z², which of the following must be true
Ⅰ.x＞z
Ⅱ.x=y+z
Ⅲ. y²+z² is a positive integer
A、Ⅰ only
B、Ⅱ only
C、Ⅲ only
D、Ⅰ and Ⅱ only
E、Ⅰ and Ⅲ only

网考网参考答案：E
网考网解析：
Statement Ⅰ must be true, because if all three variables are positive integers and x 2 =z 2 plus the square of another positive integer, then x has to be greater than z;, plug in numbers to verify. Ⅲ must be true because the square of a positive integer is always a positive integer, and y 2 +z 2 is equal to the square of a positive integer (i.e.=x 2 ). Ⅱ does not have to be true because if you square both sides of x=y+z, you get x 2 =y 2 +2yz+z 2 , which does not agree with the original statement. document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>