Which system of equations has one solution?

Write an equation of the line given the two points below (write your equation in slope-intercept form, y=mx+b): (-4, 4) and (6, -4)

Which is the equation of an ellipse with directrices at x = ±4 and foci at (2, 0) and (−2, 0)?

For the rule of 78, for a 12-month period, the last term in the sequence is 12 and the series sums to 78. for an 10 month period, the last term is and the series sum is . for a 15 month period, the last term is and the series sum is . for a 20 month period, the last term is and the series sum is