If two linear equations, y = x + 4 and y = 2x + c, intersect at x = 1, find c.

Draw the two equations, indicating the point of intersections (whiteboard).If the lines intersect at x=1, then at that point the y values of each equation are equivalent. Therefore, x+ 4 = 2x + c.Inputting x=1, (1)+4 = 2(1) + c, which is the same as 5 = 2 + cThe answer follows as c = 3.