1.小明把2條長度的鐡線分別做成了一個長方形和一個正方形.
a.如果長方形長a cm 及闊b cm,試用a和b表示正方形的邊長.
b.如果該長方形的長度比闊度長9cm,求正方形與長方形的面積之差.
請詳細....說明
因式分解...10分
2010-06-03 3:18 am
回答 (2)
2010-06-03 3:25 am
2010-06-03 9:28 pm
1a. 長方形長a cm 及闊b cm，所以鐡線的長度＝2(a+b)，因為正方形的邊長＝闊，所以正方形的邊長=[2(a+b)] / 4
=(a+b) / 2
b.如果該長方形的長度比闊度長9cm, so the width b cm is (a+9) cm
The area of the rectangle is a(a+9)cm square.
since the length of square is (a+b) /2
therefore the area of the square is [(a+b) /2] *[(a+b) /2 ]
put b = a+9 in the equation.
Therefore, [(2a+9)/2] *[(2a+9)/2]
=(4a^2+36a+81)/4
正方形與長方形的面積之差:
=(4a^2+36a+81)/4 - a(a+9)
= a^2-a^2+9a-9a+ 81/4
=81/4
=(a+b) / 2
b.如果該長方形的長度比闊度長9cm, so the width b cm is (a+9) cm
The area of the rectangle is a(a+9)cm square.
since the length of square is (a+b) /2
therefore the area of the square is [(a+b) /2] *[(a+b) /2 ]
put b = a+9 in the equation.
Therefore, [(2a+9)/2] *[(2a+9)/2]
=(4a^2+36a+81)/4
正方形與長方形的面積之差:
=(4a^2+36a+81)/4 - a(a+9)
= a^2-a^2+9a-9a+ 81/4
=81/4
參考: myself
收錄日期: 2021-04-23 20:45:20
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https://hk.answers.yahoo.com/question/index?qid=20100602000051KK01180