pdf("rpd2_9.pdf")

A <- matrix(c(1,1,1,-1,0,1,-1,2,-1),byrow=T,ncol=3)

y1 <- matrix(c(3,10,20),ncol=1)

y2 <- matrix(c(6,14,21),ncol=1)

x1 <- A %*% y1

x2 <- A %*% y2

lengthA <- sqrt(A %*% t(A))

Astar <- solve(lengthA) %*% A

x1star <- Astar %*% y1

x2star <- Astar %*% y2

A

y1

y2

lengthA

Astar

x1star

x2star


dev.off()