4 a) The line y=x-l intersects the circle x² + y² = 25 at two points. This line is called a "secant". Find the coordinates of the two points of intersection. b) For what value(s) of "k" will the line y=x+k be a tangent to the circle x² + y² = 25 ? Recall: a "tangent" is a line that touches a circle at exactly one point. Note: You must do BOTH parts of question 4, if you choose to answer this question.