Non understanding of concepts

#1

here i dont understand clearly the purpose of ones matrix ?? what is its use?

#2

As you most remember, the equation of the line we are following is given by theta(transpose)*x. Here, the would be a theta(0) value which will represent the bias term for the equation of the line. The value of x which gets multiplied by this value of theta, i.e., x(0) must be 1. Thus, for this reason we add a ones row with shape equal to the number of examples.

I hope this clears your doubt.