The value of b is one. You just have to use the standard equation y = a + bx^2 + c. Get a, b, then c and from the given equation above you can derive a formula which is x is equal to the - b over 2 multiplied by a. if you get the value of x then substitute it to the equation and you will now get the value of b.
The next term in the sequence will be increased by 27.
The difference between 15 and 34 is 19
The difference between 34 and 55 is 21
The difference between 55 and 78 is 23
The difference between 78 and 103 is 25
Following this pattern, the next number will be 130
I think is
y = x - 1y = 3x - 9
y - y = x - 3x = -9
0 = - 2x = - 9
