Question

Q:Q

求解

20. 已知y是x的一次函數,當x=1、5時,其函數值之和為20;當x=11、15時,其
函數值之和為30。當x=20時,其函數值為何?
(A)17.5
(B)18.5
(C)19
(D) 20
X²L
X
- 6x
X
-26
17 165

Answer 1

✨ 最佳解答 ✨

Ny-Ålesund

y = ax + b

(a + b) + (5a + b) = 20
(11a + b) + (15a + b) = 30

6a + 2b = 20...(1)
26a + 2b = 30...(2)

20a = 10, a = 1/2
b = 17/2

y = 1/2 x + 17/2
x = 20
y = 10 + 17/2 = 37/2