Question

Second degree trend function is shown as y= a + bx + cx^2 in general. With considering the coefficients of trend functions given below, draw the representative graphs of variable y about trend and interpret generally.

y= a + bx + cx^2

y= a+ bx – cx^2

y= a – bx + cx^2

y= a – bx – cx^2

Answer 1

Hence , we observed that when the values of a, b and c changes, the graph changes as-

- if the Value of 'a' changes then y-intercept changes i.e. y-intercept = a

- if the Value of 'b' changes then its axis changes as greater the Value of b , its vertex goes down towards negative y-axis. Also, for positive sign with 'b' gives the graph is on negative side of x-axis and for negative sign with 'b' gives the graph is on positive side of x-axis.

- if the Value of 'c' changes then its slope on any point increases as c increases, and on decreasing the Value of c , slope also decreases. Also, for positive sign with 'c' gives the graph facing upward open and for negative sign with 'c' gives the graph facing downward open.