.BG
.FN backsolve
.TL
Backsolve Upper-Triangular Equations
.CS
backsolve(r, x, k=ncol(r))
.AG r
square, upper triangular matrix.
.AG x
right-hand sides to equations.
.AG k
number of columns of `r' to use in solving the system.
.RT
matrix like `x' of the solutions `y' to the equations `r %*% y == x'.
.PP
The lower triangle of `r' is not looked at (in particular, it
does not need to be zero).
.SA
suitable `r' matrices can be obtained from `chol' and `qr'.
.KW array
.KW algebra
.WR
