Nonlinear Functions

Question

In the xy-plane, the graph of y=−2x²+9x intersects the graph of y=x at the points (0,0) and (c,c). What is the value of c?

Answer 1

If two lines intersect then the coordinates of the intersection solve both equations.

x = -2x² + 9x

0 = -2x² + 8x

0 = -2x(x - 4)

x = 0 or x = 4