A ladder is resting against a wall. The top of the ladder touches the wall at a height of 15feet. Find the distance from the wall to the bottom of the ladder if the length of the ladder is one foot more than twice its distance from wall.
有把梯靠住個牆.把梯最尖點住個牆係15ft高.找佢geh距離由個牆底去到最底geh梯.把梯長度係2x+1geh距離由個牆底去到最底geh梯!
要用quadratic fomula黎計!
中英okay!
algebra!10pts
2008-04-17 10:40 pm
回答 (2)
2008-04-17 11:21 pm
✔ 最佳答案
Let x be the distance from the wall.length of ladder = 2x+1
(2x+1)^2 = x^2 + 15^2
4x^2 + 4x + 1 = x^2 + 225
3x^2 + 4x - 224 = 0
(3x+28)(x-8) = 0
x = -28/3 (rejected) or x = 8
Therefore, length of ladder = 8 feet
2008-04-17 11:21 pm
Let X be the distance from the wall to the bottom of the ladder.
Then:
15^2 + X^2 = (2X + 1)^2 (畢氏定理)
225 + X^2= 4X^2+4X+1
3X^2 + 4X - 224 = 0
(3x + 28) (X - 8) = 0
Then X = -28 or X = 8
Reject the answer -28
Ans : X = 8
i.e. the distance from the wall to the bottom of the ladder is 8ft
2008-04-17 15:22:16 補充：
X = -28/3
Then:
15^2 + X^2 = (2X + 1)^2 (畢氏定理)
225 + X^2= 4X^2+4X+1
3X^2 + 4X - 224 = 0
(3x + 28) (X - 8) = 0
Then X = -28 or X = 8
Reject the answer -28
Ans : X = 8
i.e. the distance from the wall to the bottom of the ladder is 8ft
2008-04-17 15:22:16 補充：
X = -28/3
收錄日期: 2021-04-14 19:07:44
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