solves a degree two polynomial
Description
This function returns the root (or two roots) of
the equation ky*y + kx2*x^2 + kx*x + kk = 0
.
When dx
is not null, it is supposed to give
the interval where the root lies, in that case only
one root is returned.
The first parameter can be a vector of any
length and all computations are vectorized.
Only real roots are considered.
Usage
1 2 
solve8quadratic(y,ky,kx2,kx,kk,dx=NULL,x0=NULL,monitor=rbsa0$monitor$v)

Arguments
y 
Vector of values for which the equation must be satisfied. 
ky 
Coefficient for 
kx2 
Coefficient for 
kx 
Coefficient for 
kk 
Constant coefficient. 
dx 

x0 

monitor 
List of constants indicating the monitoring choices, see the 
Details
When dx
is defined only one root is returned,
belonging to the interval; if it is not possible (root(s)
exist(s) and do(es) not comply) a fatal error
is issued.
When every real number complies with the equation, according
to available arguments, the returning value is x0
,
mean(dx)
or 0
.
When is.null(dx)
either one or two roots is
returned with NA
when the solution is complex.
Value
A matrix having one or two columns according to the values of
ky,kx2,kx,kk,dx
.
Examples
1 2 3 4 
solve8quadratic(1:10, 1,1,0,20);
solve8quadratic( 3,1,1,1, 1);
solve8quadratic( 3,1,1,1, 1,c(0.5,1.5));
