GRE考试

【单选题】


If a and b are the lengths of the legs of a right tri-angle whose hypotenuse is 10 and whose area is 20, what is the value of (a + b)²A．100
B．120
C．140
D．180
E、200

网考网参考答案：D
网考网解析：
Expand: (a + b) 2 = a 2 + 2ab + b 2 = (a 2 + b 2 ) + 2ab. By the Pythagorean theorem, a 2 +b 2 = 10 2 =100; and since the area is 20, [*] Then (a 2 +b 2 )+2ab= 100+80=180. [*] document.getElementById("warp").style.display="none"; document.getElementById("content").style.display="block"; 查看试题解析出处>>