if( !require('NLRoot') ){
    install.packages('NLRoot')
}
library(NLRoot)

# Plot the region where the argument of the square root is positive:
# 
x = seq( -2, 1, length.out=100 )
y = function(x){ 2*(1-x)*exp(x) - 1 }
ys = y(x) 
plot( x, ys, type='l' )
abline(h=0, col='blue')
grid()

BFfzero( y, -2.0, -1.5 )
BFfzero( y, 0.5, 1.0 )

#postscript("../../WriteUp/Graphics/Chapter2/chap_2_sect_2_prob_11_plot.eps", onefile=FALSE, horizontal=FALSE)

x = seq( -1.67, 0.75, length.out=100 )
y = function(x){ sqrt( 2*(1-x)*exp(x) - 1 ) }
ys = y(x) 
plot( x, ys, type='l', xlab='x', ylab='y(x)' )
grid()

#dev.off()