ถ้า f (1) = 3 และ f (n) = -2f (n-1) + 1, f (5) คืออะไร?

ตอบ:

# f (5) = 43 #

คำอธิบาย:

# f (1) = 3 #

# f (n) = - 2f (n-1) + 1 #

# f (2) = - 2f (1) + 1 #

# f (2) = - 2 (3) + 1 = -6 + 2 = -5 #

# f (3) = - 2f (2) + 1 #

# f (3) = - 2 (-5) + 1 #

# f (3) = 11 #

# f (4) = - 2 (f (3)) + 1 #

# f (4) = - 2 (11) + 1 #

# f (4) = - 22 + 1 = -21 #

# f (5) = - 2 (f (4)) + 1 #

# f (5) = - 2 (-21) + 1 #

# f (5) = 42 + 1 #

# f (5) = 43 #