16x+3y=251 and 8x+4y=148 then you set them up to each other and cancel one coefficient through elimination or find out what X or Y equals and substitute into either equation
Let the nth term be given by the expression an²+bn+c.
We can write A: -7=a+b+c B: -6=4a+2b+c C: -3=9a+3b+c
D: B-A: 1=3a+b
E: C-B: 3=5a+b
E-Dm 2=2a, a=1, b=1-3=-2, c=-7-1+2=-6.
So the expression for the nth term is n²-2n-6.
Put n=4: 16-8-6=2 which fits the sequence.
Put n=5: 25-10-6=9 which also fits the sequence.
So the nth term is
