[代數][謝謝老師]

[LATEX]

請問等差數列問題

dd.GIF (14.35 KiB) 已瀏覽 7587 次

[thepiano]

先把數字弄清楚吧！

[LATEX]

由上到下的數字


74
186
103

0

[thepiano]

a + 3b = 74
2a + c = 103
4a + 2e = 186

b = - (a - 74) / 3
c = 103 - 2a
e = 93 - 2a

(a + b) + (3a + d) = 2(2a + c)
d = 2c - b

(2a + c) + (4a + e) = 2(3a + d)
d = (c + e) / 2

2(103 - 2a) + (a - 74) / 3 = (103 - 2a + 93 - 2a) / 2
a = 50，c = 3，b = 8，d = -2
3a + 4d = 142