Originally Posted by
GrigOrig99 Hi, first time poster.
Q. In the sequence u1, u2, u3,…,un,
u1 = 0, u2 = 3, u3 = 12 and un = a + bn + cn^2
Find the values of a, b and c.
Attempt:
If n = 1 then u1 = a + b(1) + c(1)2 = 0
= a + b + c = 0
If n = 2 then u2 = a + b(2) + c(2)2 = 3
= a + 2b + 4c = 3
If n = 3 then u3 = a + b(3) + c(3)2 = 12
= a + 3b + 9c = 12
= a + b + c = 0
= a + 2b + 4c = 3
= a + 3b + 9c = 12
It's been a number of years since I've last studied maths. Can anyone help me on what comes next? Many thanks.