1. Get the derivative of the curve.
2. From the equation of the first tangent, we know that the gradient of the curve at x = -1 is 1.
So, in your derivative, plug in x = -1 and equate to 1.
3. So the same thing with the second tangent.
4. Solve the equations, that you just obtained, simultaneously to get the values of a and b for your original curve.