[解題] 國中數學-三角形面積
1.年級:國中 數學總複習題目
2.科目:數學
3.章節:三角形面積
4.題目:
如圖
http://www.badongo.com/pic/4660024
畫的有點簡略...
5.想法:
一開始只想到用未知數假設x y z w
然後寫出三個方程式
x*(w+z)/2=4 =>xw+xz=8
y*z /2=3 =>yz =6
w*(x+y)/2=5 =>wx+wy=10
長方形總面積
(x+y)*(w+z)=xw+yw+xz+yz
故所求面積為 長方形面積-三個已知三角形面積
=>xw+yw+xz+yz-(xw+xz)/2-yz/2-(wx+wy)/2
=yw/2+xz/2+yz/2
=yw/2+xz/2+3
未知數消不掉...
不曉得是條件不足還是我有那個點沒想到
可是國中生用到四個未知數好像也不太對?
懇請各位解答 感謝~
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