演練 3
又
24-1=7
24 = 8
7
4:4
☆已知P:P+2=5:12,求正整數的值。
解
ph: ptz 5:12
Ph: p
3 = 5:12
12 x PR 5x ph12
(n-1) (n-2) (n+2)(n+1)(?: 5:12 12n (n-1) (n-2). § (h+2) (n+1)n
5 (n+2) (n+1): 12 (n-2) (n-1)
5n² + 15 + 10 - 12 (n-3n+2)
5n² + 15 + 10 = 12n²- 36 +24
In² - 5in +14=0
(4-7)(74-27-0
1-7.7-2
=) 12 (n-1) (n-2) = 5 (n+2) (n+1) 423
7n2 51n + 14:0•) ( n. 7) (7 n. 2) .0
4.7
甲
甲
(1)
4
4!