Finding Specific Points on a graph

[ac847]

Hello, I have a line that starts off with a steady increasing slope but suddenly jumps to a very steep slope. My problem is that I need to figure out the exact point (x-axis) where that change occurs. Can anyone help with a formula or function? I already know how to solve both exact slopes, I just do not know how to find that exact point.

[shg]

Subtract adjacent x values and look for the increase.