✔ 最佳答案
直線方程為 y = mx + c
m = 1/0.5 = 2
c = 1
得 logy = (2)logx + 1
logy = 2logx + log10
logy = logx² + log10
logy = log(10x²)
y = 10x²
2014-01-08 14:52:52 補充:
T(1) = ar⁰ = a
T(2) = ar¹ = ar
T(3) = ar²
T(4) = ar³
T(5) = ar⁴
T(6) = ar⁵
T(4) + T(6) = 10
ar³ + ar⁵ = 10 ..... (1)
T(5) - T(6) = 5
ar⁴ - ar⁵ = 5 ..... (2)
2014-01-08 15:15:34 補充:
(2)/(1) ==> (ar⁴ - ar⁵) / (ar³ + ar⁵) = 5/10 = 1/2
ar³(r-r²) / ar³(1+r²) = (r-r²)/(1+r²) = 1/2
2r-2r² = 1+r²
3r² -2r + 1 = 0
[-b±√(b²-4ac)]/2a
r = [2±√4-12]/6 = [2±8i]/6 = (1±4i)/3
似乎很怪,但計算上又冇錯。 ?????????
2014-01-08 17:29:56 補充:
誰說計算上沒錯?
r = [2±√(4-12)]/6 = [2±2(√2)i]/6 = [1±(√2)i]/3
你好嘢!