問題詳情:
“囧”像一個人臉鬱悶的神情.如圖,邊長為a的正方形紙片,剪去兩個一樣的小直角三角形(*影部分)和一個長方形(*影部分)得到一個“囧”字圖案,設剪去的兩個小直角三角形的兩直角邊長分別為x、y,剪去的小長方形長和寬也分別為x,y.
(1)用含a、x、y的式子表示“囧”的面積;
(2)當a=12,x=7,y=4時,求該圖形面積的值.
【回答】
(1)a2-xy×2-xy=a2-2xy;··························································(3分)
(2)當a=12,x=7,y=4時,
原式=122-2×7×4=88 ···········································································(6分)
知識點:整式的加減
題型:解答題