#====================
# Figure 8.5.R.
# Four quadratic equations.
#====================
xhi=2
xlo=-1
x=xlo+(xhi-xlo)*(0:1000)/1000
layout(matrix(c(1,2,3,4),2,2))
y=x^2-x-1
plot(x,y,type="l",ylim=c(-2,2),lwd=2)
text(-.75,1.75,"a")
y2=numeric(length(x))
points(x,y2,type="l",lty="dashed")
y=-x^2+x+1
plot(x,y,type="l",ylim=c(-2,2),lwd=2)
text(-.75,1.75,"c")
points(x,y2,type="l",lty="dashed")
y=x^2-x+1
plot(x,y,type="l",ylim=c(-2,2),lwd=2)
text(-.75,1.75,"b")
points(x,y2,type="l",lty="dashed")
y=-x^2+x-1
plot(x,y,type="l",ylim=c(-2,2),lwd=2)
text(-.75,1.75,"d")
points(x,y2,type="l",lty="dashed")